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March 16th, 2013, 01:05 PM  #1 
Newbie Joined: Mar 2013 Posts: 2 Thanks: 0  Statistics: 90th percentile
I'm a little confused on how you would do something like this: I have a cumulative probability distribution H(x): 0 0.31042 1 0.67825 2 0.89149 3 0.97196 4 0.9942 5 0.999 6 0.99985 7 0.99997 8 1 and I need to find the 90th percentile of demand.. I understand that this means its the minimum x so that H(x) >= 90% but I need an example to make sure I'm doing this right. Would this mean x >= 3 in this case?? 
March 17th, 2013, 12:40 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,823 Thanks: 723  Re: Statistics: 90th percentile
It depends on whether x is a discrete variable or continuous. Your answer is correct for discrete. However if x is continuous you need to estimate (interpolation) what value of x corresponds to H(x) = 0.9.


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