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Re: Basic normal and t table questions

• To: mathgroup at smc.vnet.net
• Subject: [mg110061] Re: Basic normal and t table questions
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 30 May 2010 23:48:14 -0400 (EDT)

Use InverseCDF

dist = NormalDistribution[187000, 2181.9716];

1 - CDF[dist, 190000]

0.0845807

InverseCDF[dist, 1 - %]

190000.

Needs["HypothesisTesting`"]

StudentTPValue[-0.1373, 6, TwoSided -> True]

TwoSidedPValue->0.895285

InverseCDF[StudentTDistribution[6],
 (1 - TwoSidedPValue/2) /. %]

0.1373

Since it is two-sided, the sign is meaningless


Bob Hanlon

---- Canopus56 <canopus56 at yahoo.com> wrote: 

=============
I am taking an intro to stats class and am trying to learn some Mathematica functions related to basic statistics. 

I would like to use Mathematica to calculate exact values and inverse values from the standard normal table and Student's t distribution table.

For example, the following returns the cdf equvialent to standard normal distribution table for a known mu, sigma (STD) and target x-bar: 

(1 - CDF[NormalDistribution[187000, 2181.9716], 190000])

The following returns the two-sided t-distribution value for a known z-statistic: 

StudentTPValue[-0.1373, 6, TwoSided -> True] 

Q1) How do I get the inverse of these, which the equivalent of reading a cdf table and a t-distribution table backwards, i.e. - 

a) Given a cdf, how do I return the z-statistic from a standard normal distribution? 

b) Given a P-Value and sampling distribution size, how did I return the z-star critical test value? 

Thanks - Kurt