1. C

    Solving normal distribution using integration and not the table

    The question is: If a normal distribution with mean mu and variance > 0 has 46th percentile equal to 20*sigma, then what is mu in terms of standard deviation? I know the answer should be mu = 20.1*sigma by solving using the standard normal table, but I need to solve it using integration.
  2. P

    Check my work on finding sigma given percentile

    I have X, a normally distributed random variable with mean 4. If 80th percentile of X = 4.8, then sigma = ? I did .80 = (4.8-4)/sigma then solved for sigma I got sigma = 1. Just wanted someone to check since it equaling 1 doesn't make sense to me.
  3. M

    Normal Distribution Percentile Calculator

    Given mean, standard deviation, and a percentile, this determines the percentile ranking. Percentile for Normal Distribution Calculator
  4. S

    Help me find the percentile please?

    Find the percentile rank A teacher gives a 20-point test to 10 students. Find the percentile rank of a score of 12. 18, 15, 12, 6, 8, 2, 3, 5, 20, 10 can you please show me the steps to solving this and don't use any complicated math terms? thanks.
  5. S

    Percentile Versus Exceedance .. whats the difference?

    Hi there, I am a student hoping to get into engineering. I havent had much formal math education in the way of probability of statistics, but I've been trying to teach myself using free online resources. I am hoping all you experts out there can help me with my problem! I am looking at wind...
  6. B

    How to find a value for the 90% percentile

    Given: Average value of gas mileage for commuter vans is: 18 mi/gal Find: What gas mileage would represent the 90th percentile if the average is 18 mi/gal? Solution: So far I have found the corresponding z-score for 90% to be 1.28. However I am having difficulty with the problem because it...
  7. D

    Percentile Dice Equation

    I came across a game that bet fake coins on a percentile die generated through a program. A computer program can not technically be random; therefore, with enough data an equation should be plausible. The die rolls a number 1-100 each time, and any number 56 and under loses. Any number 57 or...
  8. N

    finding percentile rank of a lightbulb that failed at 9000 hours

    finding the percentile rank of a lightbulb that failed at 9000 hours I'm trying to find the approximate percentile rank of a lightbulb that failed at 9000 hours (based on the information from the problem below), but I'm not sure how to solve this... A consumer product testing lab tested 400...
  9. J

    Z-Score to Percentile Formula?

    I am looking for a formula to convert a z-score into the percentile or confidence interval. for example a z-score of 1 would give 68%, a z-score of 2 would give 95% what is the formula/equation for this? I do not want to use an online z-score to percentile calculator, and I do not want to use...
  10. L

    Percentile Determination, given: mean, median, standard deviation

    Hello all, I have a question about determining percentile on a test. I am given mean (77%), median (78%), and standard deviation (8). I scored a 74%, and there were 102 test takers. If possible, could you explain to me how to calculate my rank on the test or percentile? Thanks so much!
  11. L

    n-th percentile

    I need to find 10th percentile of random variable X with PDF defined with: f(x) = \left\{\begin{array}{cc}c(x-x^3)&0< x < 1\\0&x\le 0 \vee x\ge 1 \end{array}\right. where c\in \mathbb{R} is const that should be found too. By integrating f from 0 to x I got cumulative dist. function...
  12. S

    percentile help with CDF

    I need to understand part b. how did they get n(p) in other words, how did they go from p = F(n(p)) n(p) see the attachment!
  13. S

    percentile help

    F(n(p)) = 2n + 2/n -4 so p = the same how does 2n + 2/n -4 become 2n^2 -n(4+p) + 2 also n= .25(4+p+(p^2 + 8)^1/2))
  14. L

    Percentile Ranges

    On a standard IQ test, the scores are normally distributed with a mean of 100 and a standard deviation of 20. a. if you score 140, in what percentile are you? b. if you score 90, in what percentile are you? So i'm pretty sure that i've got the idea behind doing questions like this however to...
  15. B


    In a distribution of 8500 parameters, if 26.7 is 56 percentile and 37.1 is 78 percentile, then what is the percentile of x (26.7 x 37), that is closest in this range? A. 1888 B. 4750 C. 6650
  16. G


    I've just a quick question about percentiles that's been bothering me. Just say, for example, that I took some test, and I got in the 95th or whatever percentile. Are there the same number of people in the 95th percentile as there are in, just say, the 63rd percentile? Basically, does each...
  17. P

    Percentile Math Problem

    Suppose that this table is shown and the question asks for a criteria on calculating the average: 5th Percentile - 50 15th Percentile - 100 Q1 = 300 Q2 = 400 Q3 = 600 85th Percentile = 650 If I used the Chebyshev' theorem would it be correct? 1 - 1/z² = 0,5 => z= +-...
  18. angel.white

    Statistics: nth percentile

    Hi, MHF :) I'm taking stats this semester, and my answer differs from my book's. I am using software called R (The R Project for Statistical Computing) My book uses software called Minitab (Statistical Analysis: Data Analysis and Statistics Software and Training | Minitab) I have two sets...
  19. D

    How to find certain percentile of X

    Given that fx(x) = 0 (x <= 10) = 10/x^2 (x >10) Find the 60-th percentile of X. How do we solve this?
  20. P


    These two questions are interrelated: For a recent standardized test, the medium was 88, Q1 was 67, and Q3 was 105... What percentage corresponds to a) the first percentile Is there an equation I can use?