Содержание
- 2. Introduction Suppose you want to answer the following questions: Does a new headache medicine provide the
- 3. T-tests can be used to answer all of these questions. There are three main types of
- 4. One-Sample T-test A one-sample t-test is used to compare a sample to an average or general
- 5. Matched Pairs T-test A matched pairs t-test usually involves the same subjects being measured on some
- 6. Two-Sample T-test A two-sample t-test compares two groups on some factor. For example, one group could
- 7. One-sample T-test in SAS We want to test whether a new headache medicine provides a relief
- 8. Type the following code in SAS:
- 9. Tests for Normality The histogram shows most observations falling at the peak of the normal curve.
- 10. SAS Code for a One-Sample T-test The code is telling SAS to run a t-test procedure
- 11. SAS Output for One-sample T-test
- 12. Interpreting Output From the SAS output, you can see that the mean relief time of the
- 13. Conclusion If alpha = 0.05, then our p-value is greater than alpha. Therefore, we fail to
- 14. Matched Pairs T-test in SAS We want to determine whether a weekend study session improves students’
- 15. Type the following code into SAS and run the program
- 16. Tests for Normality There are so few data points that the histograms are difficult to interpret.
- 17. SAS Code for Matched Pairs T-test PROC TTEST DATA = study; TITLE “Example of Program for
- 18. SAS Output of a Matched Pairs T-test
- 19. Interpreting Output The difference of the mean score (d-bar: before-after) is -7.33; on average the scores
- 20. Conclusion If alpha = 0.05, then the p-value
- 21. Two-Sample T-test in SAS We want to determine whether a new headache medicine provides a different
- 22. Type the following code into SAS and run the program:
- 23. A few notes: Notice the variable “group” is followed by a “$” because it is a
- 24. Tests for Normality The tests for normality for both the treatment and control groups are non-significant
- 25. Histograms for control and treatment groups
- 26. SAS Code for Two-Sample T-test Notice for a two-sample t-test you must specify what distinguishes the
- 27. SAS Output for a Two-Sample T-test
- 28. Interpreting the Output: Pooled vs. Unpooled Variance Before you can interpret your test statistic and reach
- 29. SAS conducts a formal F-test to determine whether the two groups have equal variances: Ho: σ12
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