| # | | Date Added | Question | Helpful Rating | Tags |
| 516 |
 |
11/19 |
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. | | T score, Percent Score, Z-Score |
| 502 |
|
11/7 |
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. | | Confidence Intervals, TDIST, t-test, Z-Score |
| 500 |
|
11/7 |
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? | | Percent Score, Area between, Z-Score |
| 494 |
|
11/4 |
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. | | Z-Score, Area between |
| 493 |
|
11/4 |
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. | | Empirical Rule, Z-Score, Unusual Event, Percent Score |
| 484 |
|
10/25 |
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 | | Z-Score, Area between, Percent Score |
| 476 |
|
10/13 |
Does normal distribution is something to do with Altman Z-Score? | | Altman Z-Score, Z-Score |
| 464 |
|
10/7 |
How do you know when to use a t-score instead of a z-score and vice versa? | -0 | Z-Score, t-score |
| 462 |
|
10/6 |
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 | | Z-Score |
| 459 |
|
10/5 |
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 | | Percent Score, Percentile, Z-Score |
| 428 |
|
9/29 |
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? | | Z-Score |
| 423 |
|
9/28 |
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? | | Z-Score |
| 420 |
|
9/28 |
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%. | | Z-Score |
| 417 |
|
9/27 |
Could you detail the value of using standard scores (Z scores) to compare relative performance of individual test scores. | | Z-Score |
| 409 |
|
9/24 |
What is the height of a man with the z score of -1.7? | | Z-Score |
| 401 |
|
9/20 |
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? | | Z-Score, Unusual Event |
| 397 |
|
9/19 |
mean score 100,standard deviation 20, z score-5 , what is the raw score? | | Z-Score, Raw Score from Z-score |
| 390 |
|
9/18 |
How do you find the normal distribution when the mean is 50 witha standard deviation between scores of 32 and 47? | | Area between, Z-Score |
| 389 |
|
9/18 |
How do you dertermine a z-score for continuous data? | | Z-Score |
| 385 |
|
9/16 |
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% | | Z-Score |
| 381 |
|
9/13 |
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? | | Z-Score |
| 379 |
|
9/11 |
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? | | Interquartile Range, Z-Score |
| 378 |
|
9/10 |
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? | | Z-Score |
| 370 |
|
9/6 |
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. | | Area between, Z-Score |
| 367 |
|
9/5 |
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 | 37.14 | Area between, Z-Score |
| 358 |
|
8/25 |
In the same set of data,can two or more elements have the same z score. | | Z-Score |
| 356 |
|
8/24 |
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. | | Area between, Z-Score |
| 349 |
|
8/15 |
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? | | Z-Score |
| 348 |
|
8/15 |
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. | 100 | Z-Score |
| 334 |
|
8/10 |
find the z value so that 20% of the standard normal curve lies to the right of Z | | Z-Score |
| 333 |
|
8/10 |
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) | | Z-Score |
| 318 |
|
8/6 |
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. | 100 | Area between, Z-Score |
| 299 |
|
7/30 |
random variable x is normally distributed with mean of 250 and standard deviation of 50 find z-score for x=175 | | Z-Score |
| 295 |
|
7/28 |
How can I calculate a Z score with only the mean and the standard deviation? | | Z-Score |
| 294 |
|
7/28 |
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? | | Z-Score, Percentile, Percentile Rank |
| 293 |
|
7/28 |
How can you use a Z score to interpret data in a school | | Z-Score |
| 290 |
|
7/25 |
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? | 100 | Z-Score, 1-sample t-test, 1-sample Z-test, Standard Error of the Mean |
| 289 |
|
7/25 |
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. | 100 | Z-Score, IQ Score |
| 283 |
|
7/19 |
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. | | Z-Score, Area between |
| 277 |
|
7/14 |
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 | | Z-Score |
| 275 |
|
7/11 |
The lowest 25% of the normal distribution falls below what z-score and t-score | 79.29 | T score, Z-Score |
| 269 |
|
7/9 |
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. | | Z-Score, Binomial Probability, Normal Approximation, binomial, BINOMDIST |
| 262 |
|
7/3 |
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. | | Z-Score |
| 260 |
|
7/1 |
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? | | Z-Score |
| 253 |
|
6/26 |
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? | | Z-Score |
| 249 |
|
6/24 |
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? | | Z-Score |
| 247 |
|
6/24 |
Jeff:
Can you possibly share the actual formula you are using in this application to produce the Adjusted Wald calculations?
Thanks | | Adjusted Wald, Z-Score, Confidence Intervals |
| 239 |
|
6/16 |
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? | 81.43 | Z-Score |
| 233 |
|
6/13 |
Between what two values of Z will 88% of the middle data values fall between? | | Z-Score |
| 232 |
|
6/12 |
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 | | Z-Score |
| 230 |
|
6/11 |
a score that is 8 points above the mean corresponds to a z-score=0.05 What is the population standard deviation? | | Standard Deviation, Z-Score |
| 219 |
|
6/6 |
A z score of 1.04 shows a percentage value of? | 75 | Z-Score |
| 210 |
|
5/29 |
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? | 87.14 | Z-Score |
| 207 |
|
5/24 |
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? | 75.71 | Z-Score |
| 206 |
|
5/24 |
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 | | Z-Score |
| 205 |
|
5/22 |
Find the number z that has cumulative proportion 0.8 | | Z-Score |
| 204 |
|
5/22 |
What does a z value mean? | 75 | Z-Score, Z-value, Standard Score |
| 202 |
|
5/21 |
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. | 71.79 | Z-Score |
| 186 |
|
5/9 |
how does altman build z-score? please send to my email the process of building this score! | | Altman Z-Score, Z-Score |
| 177 |
|
5/2 |
Find the probability that a randomly selected adult has an IQ that is less than 130 | 84.29 | IQ Score, Z-Score |
| 176 |
|
4/30 |
In a 0ne-tail test (l side) with z score of 1.645, what are the percentages for critical value and non-critical value? | 82.86 | One-Tailed Area, Z-Score, Critical Value |
| 173 |
|
4/27 |
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? | 100 | Z-Score |
| 170 |
|
4/25 |
If last six month average defect rate is 5% then what will be the process Zst score?
| | 1.5 Sigma Shift, Z-Score, Z Short Term |
| 161 |
|
4/21 |
z Scores lenths are measured in centameters, does it have to be converted to a different unit of measurment? | | Z-Score |
| 157 |
|
4/17 |
With a z score of 1.5, what percentage often scores are above 52 and what percentage of the scores are above 60? | 100 | Z-Score |
| 146 |
|
4/9 |
what is the z-score that corresponds to the 20th percentile of the normal distribution | 42.14 | Z-Score, Percentile |
| 137 |
|
4/4 |
What score would Sandra need to beat 91 percent of her mathematics class? The mean score was 73, and the standard deviation was 12. | 96.43 | Z-Score |
| 135 |
|
3/31 |
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)?? | | Z-Score |
| 128 |
|
3/25 |
what is the value of z score required for a 70% confidence interval? | 50 | Z-Score, Confidence Intervals |
| 114 |
|
3/16 |
The mean on this test is 3.5 with a standard deviation of .5. Billy scores 5. What is the standard score? | 100 | Standard Score, Z-Score |
| 96 |
|
3/1 |
The mean is ì = 60.0 and the standard deviation is ó = 4.0.
Find the probability that X is less than 53.0. | | Z-Score |
| 70 |
|
12/10/07 |
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. | | Z-Score, Percentile |
| 48 |
|
10/29/07 |
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 | | Z-Score |
| 42 |
|
10/29/07 |
What are the units of z-score? | | Z-Score, Units of Measure |
| 41 |
|
10/29/07 |
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? | | Z-Score, Standard Normal Curve |
| 39 |
|
10/29/07 |
What is the basic formula for the z-score other than table of areas? | | Newton-Raphson, Z-Score |
| 38 |
|
10/29/07 |
Alexa got 144 on her test which has a mean of 128 and a standard deviation of 34. What is her z-score? | 98.57 | Z-Score, example |
| 37 |
|
10/29/07 |
How do you calculate the z score for the raw score of 10 based on the following distribution: 8, 9, 15, 30, 7, 8 ? | 100 | Z-Score, Standard Deviation |
| 33 |
|
10/29/07 |
How do you find a z score such that 8% of the area under the curve is to the right of Z? | 95.71 | Z-Score, One-Sided Area |
| 29 |
|
10/29/07 |
How do you calculate a z-score on discrete data? | | Z-Score, Discrete Data |
| 26 |
|
10/29/07 |
How do you calculate z-scores from batting averages? | | Z-Score |
| 25 |
|
10/29/07 |
What does a Z-score look like on a graph? | | Z-Score |
| 17 |
|
10/29/07 |
Having obtained the z score and then derived the percentage... what does the percentage tell you? | 61.43 | Unusual Event, Z-Score |
| 15 |
|
10/23/07 |
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
| 100 | DPMO, Z-Score, Process Sigma, Z-upper |
| 14 |
|
10/23/07 |
What percent of the time should this occur? (Z-Score) ? | 42.14 | Z-Score, Normally Distributed, Standard Deviation, Normal Curve |
| 13 |
|
10/23/07 |
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? | | Z-Score, Unusual Event |
| 12 |
|
10/23/07 |
Can a z score be calculated by input of a proportion only? | 100 | Proportion, Z-Score |
| 11 |
|
10/23/07 |
What is the z value for 1.648? | 78.57 | Z-Score |
| 10 |
|
10/23/07 |
What is the difference between a Z-Scores and Process Sigma? | 59.14 | Process Sigma, Z-Score, 1.5 Sigma Shift |
| 4 |
|
10/23/07 |
Where can I find a Z score chart ? | 100 | Z-Score |
| 3 |
|
10/23/07 |
What is the critical z score for a one tailed test with alpha = .01. | 87.14 | Alpha, Z-Score |
| 2 |
|
10/23/07 |
Joe received a z score of -1.50 on a classroom test. This means that, compared to his classmates, Joe's score was...? | 45.71 | Z-Score, 1.5, lambda |
