Quantitative Usability, Statistics & Six Sigma by Jeff Sauro
Z-Score to Percentile Calculator
by Jeff Sauro | December 3, 2007 ::
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Enter a z-critical 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. To convert a percentage into a Z-Score use the Percentile to Z-Score Calculator.
Download this calculator in an excel file or take a Crash course in Z-scores
Watch a Short Demo
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Percentile to Z-Score CalculatorInteractive Graph of the Standard Normal Curve
| April 12, 2010 | saleh wrote: |
| Hi, This calculation assumes a normal distibution of scores, right? Lets say that I got a score of 404 in an exam and the mean is 271 and the SD is 50. The z-score will be 2.66 (z=x-m/sd). Can I caluculate the percentile corresponding to the score of 404 without assuming a normal distribution of the scores? Thank you |
| April 5, 2010 | Danielle Rice wrote: |
| I'd like to know what numerical method is used to calculate probabilities. Thanks |
| March 25, 2010 | anonomous wrote: |
| thank you very much helped a lot in my hw |
| March 8, 2010 | Aditi M Sengupta wrote: |
| 5. The Maine Education Assessment (MEA), a test completed annually by all students in the state in select grades, has M = 250 and SD = 50. What MEA score separates the upper 30% of the cases from the lower 70%?(EDPS 621, Eastern Michigan University, Winter, 2010) |
| March 3, 2010 | Janella annabella Shontella Ivonovich wrote: |
| math should go die. |
| March 3, 2010 | Percepicia wrote: |
| is there anyway you can show us how to actually do math problems??? and not just tell us the answer???? k. thanks. percepicia |
| January 26, 2010 | Stephanie wrote: |
| Thank you so much for this incredibly handy tool!It's so appreciated! |
| January 9, 2010 | anonomous wrote: |
| perfect. |
| November 12, 2009 | Peter Belamarich wrote: |
| great |
| November 6, 2009 | Kathy wrote: |
| The pictures are helpful--made me more certain I was using it correctly. I compared the answers to a z-table and both gave the same answer (for 1-sided), so I felt confident I was getting using the info correctly. I don't understand the statistics, just needed to be able to convert a Std Deviation Score to a Percentile for a market potential calculation. |
| September 30, 2009 | Sam wrote: |
| What was the formula that you used to find the area associated with each z-score? |
| 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 |