A researcher randomly assigns volunteers into two groups: group 1 (control group) takes an exam after sleeping less than 8 hours the night before the exam, whereas group 2 (experimental group) gets 8 or more hours of sleep the night before the
exam. All students took the exam. The researcher uses a computer statistical software package to compare the mean score of subjects in group 1 and group 2. This results in statistics of t = 2.84, degree of freedom (50 + 50 = 100 – 2) = 98, and p =.03. Which statistical test, if any, was conducted in this study? 1. An independent sample t test.
2. A dependent sample t test.
3. A nursing student t test.
4. An analysis of variance or ANOVA.
1
Rationale 1: The first clue should be the statistic of t =. However, this just tells you it is a t test, not which type of t test. There are two additional clues to help you figure out whether it is an independent sample t test. The most obvious is the fact that there are test scores for two independent groups. The last clue is the degree of freedom. The formula for df is (n + n) -2 for independent sample t test but N - 1 for dependent or paired t test. In this case, a small n represents the sample of each group and the capital N represents the sample size of the entire study.
Rationale 2: A paired or dependent sample t test usually has two measures on one group–a before and an after measure.
Rationale 3: There is not a common statistical test with this name.
Rationale 4: ANOVAs are reported as F values not t values.
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