Re: st: Output differences, Stata 11 vs Excel 2010

[<richgold@ix.netcom.com>]

you do not tell us what you did (e.g., what was your exact Stata command); since, using -ttesti- on the last row of the Stata set below, I do not match your results (i.e., your p-value), you need to provide more information

Rich

-----Original Message-----
>From: Yerik Kaslow <yerik.kaslow@gmail.com>
>Sent: Nov 1, 2013 2:26 PM
>To: "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
>Subject: st: Output differences, Stata 11 vs Excel 2010
>
>I apologize, copy+paste lead to sending before I had finished
>displaying the data. Sorry!
>
>Hi Statalisters,
>
>I've noticed this difference several times before, and it's always
>confused a troubled me a little.
>
>I have clinical trial data I'm analyzing, ttest output is below. The
>means are nearly the same, but the standard deviations are different.
>I've also noticed this also with p-values. The differences are always
>small, but if it's right at the margin of significance, it can
>obviously make a difference.
>
>Does anyone have insight as to why when I run tests of the exact same
>data using Stata, then using Excel, I get slightly different results?
>
>Any insight is appreciated. Thus far I've been taking Stata's output
>over Excel's. I apologize for the bunching together of the output,
>plain text mode is what it is.
>
>Thanks in advance,
>
>Excel Output:
>
>N Int N Con Total N Mean Int Mean Con Diff Int Con SD Int SD Con Pvalue =
>CD1 68 58 126 6.49 6.45 0.04 2.70 2.21 0.9344
>CD2 68 58 126 7.65 7.41 0.23 2.27 2.07 0.5539
>CD3 68 58 126 8.01 7.90 0.12 2.12 2.06 0.7542
>CD4 68 58 126 7.29 7.22 0.07 2.34 2.01 0.8597
>CD5 68 58 126 7.74 6.45 1.29 2.13 2.49 0.2262
>CD6 68 58 126 7.74 7.31 0.42 2.15 2.24 0.2841
>
>Stata Output:
>
>N Int N Con Total N Mean Int Mean Con Diff Int Con SD Int SD Con Pvalue =
>CD1 68 58 126 6.49 6.45 0.04 2.37 1.97 0.9252
>CD2 68 58 126 7.65 7.41 0.23 2.14 1.66 0.5012
>CD3 68 58 126 8.01 7.90 0.12 2.00 1.82 0.7313
>CD4 68 58 126 7.29 7.22 0.07 2.11 1.77 0.8425
>CD5 68 58 126 7.74 6.45 1.29 1.99 2.29 0.1015
>CD6 68 58 126 7.74 7.31 0.42 1.89 1.98 0.2223
>
>
>-- 
>Yerik Kaslow
>yerik.kaslow@gmail.com
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