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st: qnorm and ttest question


From   Stata <stataq@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: qnorm and ttest question
Date   Thu, 2 Feb 2012 15:10:18 -0500

Hello,

I try to see the data for "total worked hour in the past week" is
normal distribution or not. I used qnorm and got a graph which most of
dots fall on/closed to the line but the left side tail is  above the
line as "worked-hour" is always non negative.

what should I say about this distribution?

I want to do ttest on 2 groups. Is it correct that they should be
normal distribution in order ttest result to be void? Can I apply CLT
and assume them as normal distribution as my sample is greater than
20,000? I have tried the sktest and they did not pass the test.

Any advice on how to handle these problem?

Thanks.
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