R vs SAS Paired T-Test
Paired t-test Comparison
The following table shows the types of Paired t-test analysis, the capabilities of each language, and whether or not the results from each language match.
| Analysis | Supported in R | Supported in SAS | Results Match | Notes |
|---|---|---|---|---|
| Paired t-test, normal data | Yes | Yes | Yes | In Base R, use paired = TRUE on t.test() function |
| Paired t-test, lognormal data | Maybe | Yes | NA | May be supported by envstats package |
Comparison Results
Normal Data
Here is a table of comparison values between t.test(), proc_ttest(), and SAS PROC TTEST:
| Statistic | t.test() | proc_ttest() | PROC TTEST | Match | Notes |
|---|---|---|---|---|---|
| Degrees of Freedom | 11 | 11 | 11 | Yes | |
| t value | -1.089648 | -1.089648 | -1.089648 | Yes | |
| p value | 0.2992 | 0.2992 | 0.2992 | Yes |
Lognormal Data
Since there is currently no known support for lognormal t-test in R, this comparison is not applicable.
Summary and Recommendation
For normal data, the R paired t-test capabilities are comparable to SAS. Comparison between SAS and R show identical results for the datasets tried. The procs package proc_ttest() function is very similar to SAS in the syntax and output produced. proc_ttest() also supports by groups, where t.test() does not.
For the lognormal version of the t-test, it does not appear to be supported in the stats or procs package. It may be supported in the envstats package. More exploration is needed to determine whether this package will produce the expected results, and whether the results will match SAS.
References
R t.test() documentation: https://www.rdocumentation.org/packages/stats/versions/3.6.2/topics/t.test
R proc_ttest() documentation: https://procs.r-sassy.org/reference/proc_ttest.html
SAS PROC TTEST Paired analysis documentation: https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_ttest_syntax08.htm