Paired-Samples T Test
This feature requires the Statistics Base option.
The Paired-Samples T Test procedure compares the means of two variables for a single group. The procedure computes the differences between values of the two variables for each case and tests whether the average differs from 0.
Example. In a study on high blood pressure, all patients are measured at the beginning of the study, given a treatment, and measured again. Thus, each subject has two measures, often called before and after measures. An alternative design for which this test is used is a matched-pairs or case-control study, in which each record in the data file contains the response for the patient and also for his or her matched control subject. In a blood pressure study, patients and controls might be matched by age (a 75-year-old patient with a 75-year-old control group member).
Statistics. For each variable: mean, sample size, standard deviation, and standard error of the mean. For each pair of variables: correlation, average difference in means, t test, and confidence interval for mean difference (you can specify the confidence level). Standard deviation and standard error of the mean difference.
Paired-Samples T Test Data Considerations
Data. For each paired test, specify two quantitative variables (interval level of measurement or ratio level of measurement). For a matched-pairs or case-control study, the response for each test subject and its matched control subject must be in the same case in the data file.
Assumptions. Observations for each pair should be made under the same conditions. The mean differences should be normally distributed. Variances of each variable can be equal or unequal.
To Obtain a Paired-Samples T Test
This feature requires the Statistics Base option.
- From the menus choose:
- Select one or more pairs of variables
- Optionally, click Options to control the treatment of missing data and the level of the confidence interval.
This procedure pastes T-TEST command syntax.