Measuring Usability: Z-Score to Percentile Calculator

Z-Score to Percentile Calculator
by Jeff Sauro | December 3, 2007 :: 138 Related Questions How useful was this calculator?
Avg. Rating: 86 ( 299 ) | 11 Comments

Page Tags

Tag Name	#	Vote
Z-Score	72
Calculator	27
Statistics	19
Standard Score	18
Normal Curve	17
Standard Deviation	13
T score	10
Percentile	9
Probability	9
mean	3
percentile to z-score calculator	3
Raw Score from Z-score	2
-2,13	1
invNorn	1
Median	1
Stanine	1
z area	1

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Enter a z-critcal value and get the area under the normal curve (a proportion). Selecting two-sided provides the area above Z and below -Z. Selecting one side provides the area only above or below the Z-value. See also the interactive Graph of the Standard Normal Curve

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Z-Score	Percent of Area	100-Percent


Two-Sided One-Sided		Decimal Points

To convert a percentage into a Z-Score use the Percentile to Z-Score Calculator

A Note about the Calculations & Decimal Precision
The values presented in the graphs above are approximations derived from the work of Abramowitz & Stegun. If you need precision to more that 4 decimals you are encouraged to consult multiple published tables of Z-Values.

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Related Questions

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	why can you not have a z- score equaling 0/0 ? what is problematic with calcutlating a z-score for a data set of repeated entries?
	random variable x is normally distributed with mean of 250 and standard deviation of 50 find z-score for x=175
	How do you calculate a Z-score with a two-sided specification limit? What is the DPMO? I have a lower spec limit of -0.008 and an uppers spec limit of 0.008. The mean of the data is -0.00306 and standard deviation is 0.003642. What is the z-score and DPMO
	How do you calculate z-scores from batting averages?
	What percent of the time should this occur? (Z-Score) ?
	IQ tests generally have scores in which the mean is 100, and the standard deviation is 16. If your IQ score was 134, what percentage of the population would have a higher IQ than you?
	With a normal distribution of 50 and standard deviation of population =10, how do I figure out the score at the 40th percentile? How do I figure out the % of scores falling above 70? How do I figure out between what scores do the middle 50 percent of cases lie? Note N=1000
	The grades on the midterm given in a large managerial stats class are normally distibuted with mean 75 and standard deviation 9. Instructors of this class wants to assign an A to top 10%, B to the next 10%, C to next 10%, D to next 10%, and an F to all scores below the 60th percentile. Find the lowest acceptable score within each established range. For example, the lowest acceptable score for an A is the score at the 90th percentile.
	How do you find a z score such that 8% of the area under the curve is to the right of Z?
	In the same set of data,can two or more elements have the same z score.
	The total area under the curve of the standard normal distribution is not necessarily 1.0. A) True B) False
	Consider a sample with data values of 10,20,12,17, and 16. Compute the z-score for each of the five observations
	Your company asks you to compare a new advertising campaign and the old one. Sample data on the accounts as follows: Old: 40, 28, 35, 38, 31, 42, 26, 44, 29, 43 New: 29, 26, 31, 26, 28, 31, 19, 21, 27, 30 Calculate the mean, median, and mode. Calculate variance and standard deviation for each set. Calculate a 95% Confidence Interval for the two sets.
	Want a sample size of about 60 (30 controls and 30 cases). At 5% significance and 80% power.How do i determine the standard deviation and mean difference.And how do i arrive at the 60? my study design is case-control.
	There are two major tests of readiness for college, the ACT and the SAT. ACT scores are reported on a scale from 1 to 36. The distribution of ACT scores for more than 1 million students in a recent high school graduating class was roughly normal with mean = 20.8 and standard deviation = 4.8. SAT scores are reported on a scale from 400 to 1600. The SAT scores for 1.4 million students in the same graduating class were roughly normal with mean = 1026 and standard deviation = 209. Jose scores 545 on the SAT. Assuming that both tests measure the same thing, what score on the ACT is equivalent to Jose's SAT score?
	A traffic study at one point on an interstate highway shows that vehicle speeds are normally distributed with a mean of 61.3 mph and a standard deviation of 3.3 mph. If a vehicle is randomly checked, find the probability that its speed is between 55.0 mph and 60.0 mph.
	When estimating the mean of a population, how large must the sample be in order that the 95% error margin is 1/8 the standard deviation?
	A sample of 36 observations is selected from a normal population. The sample mean is 21, and the sample standard deviation is 5. Conduct the following test of hypothesis using the .05 significance level. H0: � ≥ 20 H1: � < 20 (a) Is this a one or two tailed test? (b) What is the decision rule? (c) What is the value of the test statistic? (d) What is your decision regarding H0? (e) What is the p-value? Please show me your calculations. Interpret the results.
	A telephone manufacturer wants its telescope to have standard deviation in resolution to be significantly below 2 when focusing on object 500 light-years away. When a telescope is used to focus on an object 500 light-years away 30 times, the sample standard deviation turns out to be 1.46. Stay explicit null and alternate hypothesis. Test your hypothesis at � = 0.01 level
	Each student in an experiment was told to look at 100 cars and count the number of people wearing the seat belts. The mean score for the class was found to be 44, and standard deviation =7. Now, a student reported finding 62 seat belt users out of 100. Do you think the student just made up a number rather than actually counting?
	What does a z value mean?
	If I know the T-score for those who made an A on a test is 60, the z-score for those that made a B is .5, the number of students total is 200, how can I find the number of students who made a B?
	A sample of households that subscribe to the United Bell Phone Company revealed the following numbers of calls received by each household last week. Determine the mean, median, and standard deviation of the number of calls received. 52, 43, 30, 38, 30, 42, 12, 46, 39, 37, 34, 46, 32, 18, 41, 5
	A standard I.Q. test produces normally distributed results with a mean of 100 and a standard deviation of 15. If an average I.Q. is defined to be any I.Q. between 90 and 109, find the probability of randomly selecting an I.Q. which is average.
	The mean weight of 500 students is 151 lbs and the standard deviation is 15 lbs. Assuming the weights are normally distributed, find out how many students weigh between 120 and 155 lbs.
	A classical experiment in extrasensory perception (ESP) consists of asking a subject to tell, without looking, the suit of each card in a deck of Zener cards. There are five suits in the deck so the probability of a chance match between the guess and the card is 1/5 or .20. If only chance is operating, you would expect a subject to get 20 matches in 100 guesses (.20 X 100 =20). The standard deviation for this mean of 20 is 4. What is the probability of a subject making 23 or more matches in 100 guesses? What is the probability of 27 or more matches in 100 guesses? Suppose a friend of a friend claimed to have ESP and agreed to sit just on time and guess at 100 cards. Suppose she made 36 matches. Calculate the probability of this many, or more, matches if only chance is at work, and carefully write a conclusion.
	What does percentile rank mean?
	How to convert a exam score (standard score) back to Percent score? e.g. Total of students 16, 71 76 56 79 74 72 68 75 77 61 81 75 70 77 77 67
	Olympic Track related question: You know the last 5 race times at the same distance for 8 runners competing in a race. As such, you can calculate the mean, sd, and variance for each. How would you go about calculating the % each one has of winning based on these statistics, assuming normal distribution
	What is the critical z score for a one tailed test with alpha = .01.
	The serum cholesterol levels for men in one age group are normally distributed with a mean of 185.1 and a standard deviation of 37.8. All units are in mg/100 ml. Find the two levels that separate the top 8% and the bottom 8% of this population.
	what is the difference between percentage and percentile?specially in cat like exams.
	When calculating confidence interval estimates...how is the x and standard deviation calculated?
	Annual starting salaries for college graduates with degrees in business administration are generally expected to be between $30,000 and $45,000. Assume that a 95% confidence interval estimate of the population mean annual starting salary is desired. What is the planning value for the population standard deviation (0 decimals)?
	How do you calculate a participant score if she was at the 67th percentile? I only have the standard deviation of the population and the mean. s = 27 x = 448.95
	A telescope manufacturer wants its telescopes to have standard deviations in resolution to be significantly below 2 when focusing on objects 500 light-years away. When a telescope is used to focus on an object 500 light years away 30 times, the sample standard deviation turns out to be 1.46. a.State explicit null and alternate hypotheses b.Test your hypothesis at the �=0.01 level.
	At one university, students are given z-scores at the end of the semester rather than the traditional GPAs. The mean and standard deviation of all students� cumulative GPAs, on which the z-scores are based, are 2.7 and 0.5 respectively. c. The president of the university wishes to graduate the top16% of the students with cum laude honors and the top 2.5% with summa cum laude honors. Where (approximately) should the limits be set in terms of z-scores? In terms of GPAs? What assumption, if any, did you make about the distribution of the GPAs at the university?
	How do you calculate a z-score on discrete data?
	The variable Z has a standard Normal distribution. a) Find the number z that has cumulative proportion 0.85. b) Find the number z such that the event Z
	In a recent year grade 8 Washington State public school students taking a mathematics assessment test had a mean score of 276.1 with a standard deviation of 34.4. Possible test scores could range from 0 to 500. Assume that the scores are normally distributed. a) Find the probability that a student had a score higher than 325? b) Find the probability that a student had a score between 250 and 305? c) What percentage of the students had a test score that is greater than 250? d) If 2000 students are randomly selected, how many will have a test score that is less than 300? e) What is the lowest score that would place a student in the top 5% of the scores? f) What is the highest score that would place a student in the bottom 25% of the scores? g) A random sample of 60 students is drawn from this population. What is the probability that the mean test score is greater than 300?
	z Scores lenths are measured in centameters, does it have to be converted to a different unit of measurment?
	Which type of data set can the mean not be calculated?
	Could you detail the value of using standard scores (Z scores) to compare relative performance of individual test scores.
	My local coffee house sells Colombian coffee beans to supermarkets in bags labelled 100g each. The tolerance of the automatic filling machine, leads to weights of bags being approximately Normally distributed with standard deviation 5g. The target mean weight is set at 106g (i.e. the filling machine is set at 6% overfill). Find the percentage of bags which are below the labelled weight. Show the z-score. How do i work this out?
	Discuss how t test can be employed in hypothesis testing by the use of directional vs. nondirectional hypotheses. Discuss types of research where using the t statistic may be an appropriate alternative to using a z-score.
	In one region, the September energy consumption levels for single-family homes are found to be normally distributed with a mean of 1050 kWh and a standard deviation of 218 kWh. Find P45, which is the consumption level separating the bottom 45% from the top 55%.
	On a scale from 0 to 100, the mean level of economic development among the countries in the world is 65 and the standard deviation is 10. What proportion of countries in the world have economic development scores above 80?
	A sample of PVC pipes coming off a production line were tested for pipe diameter size. The statistical results (in millimeters) were: Mean 300 Median 300 Mode 300 Standard Deviation 15 Range 90 Number in Sample 100 a) According to the Normal Rule, what percent of the pipes had diameters between 285 and 315? b) What would the range of pipe diameters need to be in order to capture 95% of the pipe diameters?
	In a 0ne-tail test (l side) with z score of 1.645, what are the percentages for critical value and non-critical value?
	How can I calculate a Z score with only the mean and the standard deviation?
	What is the difference between a Z-Scores and Process Sigma?
	Administrative staff based at a business school in the UK are advised to take a 15 minute break from their personal computer after working on it for 90 minutes continuously. A random sample of 36 staff revealed that, one average a break was taken after 97.4 minutes of continuous use. The corresponding standard deviation was measured at 5.1 minutes. a. Provide a 99% confidence interval for the population mean time for working on a PC continuously, prior to taking a break. b. Conduct a suitable test at the 1% level of significance, to see whether staff, on average, are working longer than advised.
	We have administered an anxiety test to all members of the class. The mean anxiety score is 71 and the standard deviation is 9. (higher score=higher anxiety) What percentage of people scored over 86 on the anxiety test?
	How do you dertermine a z-score for continuous data?
	What is the basic formula for the z-score other than table of areas?
	find the area under standard normal curve which lies (a) to the right of Z=1.76,(b)to the left of Z=.94,(c)to the right of Z=-.65,(d)b/w Z=.34 & Z=.62
	How can you use a Z score to interpret data in a school
	how does altman build z-score? please send to my email the process of building this score!
	Given that the traveling distance for a population of college students is normally distributed with the mean of 10 kilometers and standard deviation equal to 3: Use the normal distribution to solve the following. a) what proportion live within 12 kilometers of the campus b) what proportion live further than 15 kilometers from campus c) what distance would give the closest 10% d) what distance would give the furthest 33%
	The mean on this test is 3.5 with a standard deviation of .5. Billy scores 5. What is the standard score?
	Suppose that the scores of architects on a particular creativity test are normally distributed.What percentage of architects have Z scores. (a) above .10, (b) below .10, (c) above .20, (d) below .20, (e) above 1.10, (f) below 1.10, (g) above -.10, (h) below -.10?
	difference between a sample parameter ( X-bar and s ) and a proportion parameter ( p )?
	What is the height of a man with the z score of -1.7?
	Given a mean score of 70, standard deviation of 15,percentile of 23.Find the Z score,T score and raw score. Please explain how to work backward on a normal distribution curve given the percentile.
	An executive drives his vehicle from home to work daily. Driving times are normally distributed with a mean of 35 minutes and standard deviation of 8 minutes. What percent of days will it take him 30 or fewer minutes? What percent of days will it take him between 40-50 minutes? What percent of days will it take him between 30-45 minutes? How long will the longest 10% of the trips take?
	The mean is � = 60.0 and the standard deviation is � = 4.0. Find the probability that X is less than 53.0.
	You survey a sample of 10 college students to measure their racial prejudice using a scale of 0 (no prejudice) to 100 (extreme prejudice). Here are the scores you obtained. 10 43 30 30 45 82 12 26 24 35 Compute the mode, median, mean, and standard deviation for this sample. Is there a skew; and if so, is it positive or negative? What does this skew reveal about the dispersion in the sample.
	Where can I find a Z score chart ?
	Find the number z that has cumulative proportion 0.8
	An auditor reviewed 25 oral surgery insurance claims from a particular surgical office, determining that the mean out-of-pocket patient billing above the reimbursed amount was $275.66 with a standard deviation of $78.11. (a) At the 5 percent level of significance, does this sample prove a violation of the guideline that the average patient should pay no more than $250 out-of-pocket? State your hypotheses and decision rule. (b) Is this a close decision?
	A bank has determined that the monthly balances of savings accounts of its customers are normaly distributed with an average balance of $1200 and standard deviation of $250. What proportions of the customers have monthly balances less than $1000?
	what is the value of z score required for a 70% confidence interval?
	What score would it have taken to be in the 90th percentile in a test with a mean of 40 and standard deviation of 7
	With a z score of 1.5, what percentage often scores are above 52 and what percentage of the scores are above 60?
	A random variable X is normal distributed with a mean of 250 and standard deviation of 50. Given that X = 175, what is its corresponding z-score? Round off your answer to 2 decimal places.
	If the average price of a new home is 145,000 what is the minimum and maximum prices of the houses a contractor will need to build to include the middle 80% of the market. Assume that the standard deviation is 1500 and the variable is normally distributed.
	If you have a normal distribution of a random variable x, with a mean of 56 and standard deviation of 8: What is the probability that the random variable x will be within plus or minus 1 standard deviation of the mean?
	mean score 100,standard deviation 20, z score-5 , what is the raw score?
	Can you please direct me to a site that would have an illustration of the normal curve that also includes cumulative percentiles, Z-score equivalents, T-score equivalents, SAT scaled score equivalents, etc. thanks
	How do you calculate the z score for the raw score of 10 based on the following distribution: 8, 9, 15, 30, 7, 8 ?
	Joe received a z score of -1.50 on a classroom test. This means that, compared to his classmates, Joe's score was...?
	find the z value so that 20% of the standard normal curve lies to the right of Z
	A woman sells an average of 300 books per month, with a standard deviation of 50. Over the next ten years, how many months will she sell more than 375 books? (round to the nearest month, if necessary)
	If a distribution of test scores is normal with a mean of 78 and a standard deviation of 11, what percent of the area lies below 60
	Suppose that in NY State, 35% of voters are Democrats, 30% are Republicans, and 11% are independent. You are conducting a poll by randomly calling registered voters. In your first four calls, what is the probability that you talk to: a)all Republicans? b)exactly 2 Republicans? c)no Independents? d)all Independents? e)at least one independent?
	A test is normally distributed with a mean of 40 and a standard deviation of 7. (a) What score would be needed to be in the 85th percentile?
	Fill in the P (X=x) values in the table to give legitimate probability distribution for the discrete random variable X, whose possible values are -4, 1,2,3 and 6. Value x of X P (X=x) -4 0.13 1 0.15 2 ? 3 0.20 6 ?
	An engineer in an automotive factory wishes to know what the tire pressure is on all cars leaving the factory. She measures the tire pressure on a sample of 10 randomly selected cars as they are about to leave the plant, in psi. The results are: 32.1 32.3 32.0 30.9 31.5 32.4 32.9 33.1 32.2 31.4 Calculate a 95% Confidence Interval on these numbers
	Can the bell curve probability value be over the value of 1?
	Alexa got 144 on her test which has a mean of 128 and a standard deviation of 34. What is her z-score?
	I am confused on how to calculate a z-score. I am doing a six sigma project right now and am lost on doing the z-score. Here is the information I am provided: Calculate the average student score necessary for the district to retain its federal funding. (You may assume the standard deviation will not change). This will require some thought. Think of the z formula. You will be solving for � (average test score in the next school year.) Think about what you already know. You know the standard deviation (because we assume that the variation in test scores stays approximately the same across years.) You also know that 70% of students must meet the cut off score. Data: The following are the results from last years MEAP scores for EHS N = 1000 x = 69.7 sd = 11.55 A student must score at or above 70% on the MEAP to meet the president's cut off score Project Information: The improvement program No Child Left Behind legislation has placed emphasis on testing students, and has tied federal funding (and thus some matching state funds) to a certain percentage of students meeting or exceeding cut off scores on state level achievement tests. The challenges that face education are very interesting indeed: unlike in manufacturing (where Six Sigma methodology was originally developed) the outcome is not a product that meets stated specifications, rather it is a student who is prepared to take his/her place in society. Unfortunately, the definition of prepared is elusive. Also unlike in manufacturing, public educational institutions cannot reject the materials they receive (students) as being defective and send them back they must take students at whatever point they received them, and advance their state of preparedness. The challenge for this project revolves around Everyday High School in Normal, Michigan. Last year only 49% of the students at the high school met the cutoff score of 70% of questions answered correctly on the Michigan Educational Assessment Program (MEAP) Michigans state level test. This percentage of students meeting the cutoff score is well below the 70% of students who must meet the cutoff score for the district to continue to receive federal funding. Because losing the federal funding (approximately $2,000,000 per year) would mean cuts in programs and maybe even staff that the board of education (BOE), parents, community, students, and staff would find unacceptable, the board of education has directed you (the Six Sigma Black Belt) to conduct a project to improve the scores on next years MEAP tests.
	An aptitude test has a mean of 220 and standard deviation of 10. find the corresponding z score for: a) a test score of 232 b) a test score of 212
	The random variable x has the following probability distribution. x 1 2 3 4 5 P(x) 0.5 0.2 0.1 0.1 0.1 Find the mean and standard deviation of x.
	What is the z value for 1.648?
	What are the units of z-score?
	Explain the difference between testing a single mean and testing the difference between two means. What two assumptions must be met when one is using z test to test differences between two means? When can the sample standard deviations s 1 and s 2 be used in place of the population standard deviations s 1 and s 2 ?
	How do you calculate standard deviation?
	What score would Sandra need to beat 91 percent of her mathematics class? The mean score was 73, and the standard deviation was 12.
	Find the probability that a randomly selected adult has an IQ that is less than 130
	A woman wrote to DearAbby and claimed that she gave birth 308 days after a visit from her husband, who is in the Navy. Lengths of pregnancies have a mean of 268 days and a standard deviation of 15 days. Determine if such a length is considered unusual?
	Jeff: Can you possibly share the actual formula you are using in this application to produce the Adjusted Wald calculations? Thanks
	The lengths of pregnancies are normally distributed with a mean of 264 days and a standard deviation of 25 days. If 100 women are randomly selected, find the probability that they have a mean pregnancy between 264 days and 266 days.
	A z score of 1.04 shows a percentage value of?
	What is the difference between a population standard deviation and a sample standard deviation?
	Can a z score be calculated by input of a proportion only?
	On a police sergeants exam, the historical mean scored was 80 with a standard deviation of 20. Four offiers scored 195,175,191, and 189 respectively. Irregularity.The officers were alleged cronies of the police chief because of their scores. Convert these four offiers socres to a standardized Z-value. Do you think there is sufficient reason to question these four exam scores; and if so how did you make this determination.
	with a mean of 150 and a standard deviation of 15 what is the probability of a student having a weight of less than 178 lbs.
	How unusual is this event (Z-Score)? A department store, on average, has daily sales of $28,707.47. The standard deviation of sales is $1000. On Tuesday, the store sold $34,650.77 worth of goods. Find Tuesday's z score. Was Tuesday an unusually good day?
	The lowest 25% of the normal distribution falls below what z-score and t-score
	If last six month average defect rate is 5% then what will be the process Zst score?
	Based on information obtained from a sample of 54, a 98% confidence interval for the average profit level of regional banks is given by 67.4 million to 87.78 million. Determine the sample standard deviation of profit
	I know that 33 is the raw score of the 85th percentile. How do I determine the mean?
	Does normal distribution is something to do with Altman Z-Score?
	what is the z-score that corresponds to the 20th percentile of the normal distribution
	Annual starting salaries for college graduates with degrees in business administration are generally expected to be between $30,000 and $45,000. Assume that a 95% confidence interval estimate of the population mean annual starting salary is desired. What is the planning value for the population standard deviation (0 decimals)? __________ How large a sample should be taken if the desired margin of error is as shown below (0 decimals)? a. $500? __________ b. $200? __________ c. $100? __________ d. Would you recommend trying to obtain the $100 margin of error? _________________
	Site preparation for new housing developments for tracts of 40 houses is normally distributed with a mean of 250 workdays and a standard deviation of 25 workdays. a.Find the probability that the site will not be completed within 280 days b. The probability that the site is completed in less than 225 workdays or it takes more than 275 workdays c. Find the number of workdays that represent the probability .99 that the site is completed. d. Find the probability that the site is completed between 260 and 280 workdays.
	Dr Zak developed a test to measure depression. He sampled 100 university students to take his five item test. The group of students was comprised of 30 men and 70 women. In this group four persons were African American, six persons were Hispanic and one person was Asian. There were five yes/no questions Yes =1 and No =0. The five items are summed giving a total score of 5, where the mean was 3.5 and the standard deviation is .5. Billy scores a 5, what is his standard score ?
	What is the standard general score conversion formula? Is this the same as a z-score formula? Which leads me to ask How do you convert from one standard score to another?
	A nationally standardized test is scaled so that the normally distributed scores have a mean of 80 and a standard deviation of 10 in the population. If we have a group of 25 scores from this test, and compute the mean, what is the probability that this mean will be: a. Below 82? b. Below 76? c. Above 80?
	How do you determine the sample size for data for which the mean and standard deviation are not known?
	What does a Z-score look like on a graph?
	If Z is a standard normal variable, find the probability that z lies between 0.73 and 1.88 or P(0.73
	An aptitude test has a mean of 220 and standard deviation of 10. find the corresponding z score for: a) a test score of 232
	Individual scores of a placement examination are normally distributed with a mean of 84.2 and a standard deviation of 12.8. If a random sample of size n = 20 is selected, find the probability that the sample mean will be less than 90.0.
	the lengths of human pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days. What is the probability that a pregnancy lasts at least 300 days?
	If an A is given to a student who scores 90% or above, what would the minimum z-score be for a 300 multiple choice question test with a mean of 195 and a standard deviation of 30
	What are the 2 advantages of using Z power? If the z score is less than 0, what can be said of the corresponding raw score? If the z score is greater than 0, what can be said of the raw score? If the z score is equal to 0, what can be said of the raw score?
	1 a. with a mean of 300 and a standard deviation of 80, how high a score do you need to be in the top 30%? 1 b. What is the interquartile range for this distribution?
	a score that is 8 points above the mean corresponds to a z-score=0.05 What is the population standard deviation?
	How do you find the normal distribution when the mean is 50 witha standard deviation between scores of 32 and 47?
	Suppose that the scores of architects on a particular creativity test are normally distributed. What percentage of architects have Z scores (a) above .10, (b) below 10, (c) above .20, (d) below .20, (e) above 1.10, (f) below 1.10, (g) above -.10, (h) below -.10?
	Suppose that the scores of architects on a particular creativity test are normally distributed. What percentage of architects have Z scores? a. above .10; b. below .10
	Having obtained the z score and then derived the percentage... what does the percentage tell you?
	Between what two values of Z will 88% of the middle data values fall between?
	How do you know when to use a t-score instead of a z-score and vice versa?
	The accounting department at Weston reports that it takes two construction workers a mean of 32 hours and a standard deviation of 2 hours... Determine the z values for 29 and 34 hrs. What percent of garages take between 32 and 34 hrs to erect.
	I have a data set where n=20. My problem is to find the score at exactly the 75th percentile assuming normality. I know the formula for z-score, the mean, and the standard deviation. How do I do this problem?
	I am conducting a ring test where 6 laboratories were asked to measure protein levels in the same flour sample. I then calculated the z score for each of their results ... z score obtined ranged from 0 to 1.7. Does the higher z score indicate that the laboratories are too far away from the norm and that they need to review their process or their staff (assuming that they are using the same test procedure)??

Ask a Question

May 28, 2009 | Tom wrote:

seen a couple people ask the same question, but i'm looking for an actual formula to convert the Z-scores to percentiles. can't find anywhere on the internet that has it.

April 17, 2009 | troy percival wrote:

i am writing a database and need to make calculations to turn z scores into percentages. I am enquiring if you can help me with the formula that operates the calculator. Many thanks

March 9, 2009 | Denise wrote:

for a population with a mean of 80 and standard deviation of 12, what is the z-score corresponding to x=71?

March 3, 2009 | Susan wrote:

6. An aptitude test has a mean of 220 and standard deviation of 10. find the corresponding z score for: a) a test score of 232 b) a test score of 212

January 26, 2009 | anonomous wrote:

6. An aptitude test has a mean of 220 and standard deviation of 10. find the corresponding z score for: a) a test score of 232

October 16, 2008 | Verena wrote:

Hi, I have been using your tool to calculate percentiles from z-score values. Until like a week ago, it worked perfectly fine, but now, when I enter a z-score of 3, one-sided, the value under 100% should be the higher one (in fact, it should be close to 99). Now, however, the higher number is being reported under the % of area section - how can that be?

September 11, 2008 | Ivy wrote:

Your MS class all took the practice clinical certification exam. The following is a listing of the raw scores that you and your friends received. Compute the z scores for these raw scores where the mean is 55 and the standard deviation is 2.5. What is a �z� score? What does it tell you? Scores: 60, 72, 48, 53, 56, 51, 50.5, 59.5 x (observation) = 8 mean = 55 standard deviation = 2.5 z = Observation - Mean Standard Deviation = 8 � 55 / 2.5 = - 18.8 I don't have a book to find the z score for -18.8. I am not even sure if that is possible to get a z score for -18.8. Thank you for your help.

June 24, 2008 | Cindy Searcy wrote:

How would I figure a z-score if the mean was 11.9, the std. deviation is .4 and I want to be 95% sure that a bag of chips did not weigh 12 Oz. as specified on bag, and I weighed 30 Bags?

May 15, 2008 | Alex wrote:

hey, can send me the formula that happens in the BG?

April 30, 2008 | Steve Kelner wrote:

I can't seem to do a negative z-score. Otherwise outstanding!

March 19, 2008 | Justin wrote:

I have a normal distribution of Homeruns per week with mean 8.3 and standard deviation of 1.1. My team is projected to hit 10 homeruns in a week while my opponent's team is projected to only hit 8. What is the likelyhood of my team hitting more homeruns during the coming week? I am guessing P(8

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