A researcher randomly assigns volunteers into two groups: group 1 ...

[jazziefee]

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 = 0.03. 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

Question 2

A researcher fails to reject the null hypothesis in a study. The study was repeated multiple times and that analysis revealed that the null hypothesis should have been rejected. What occurred in the original research?
 
  1. A type I error
  2. A type II error
  3. A standard error of the mean
  4. A type III error

[dominiqueenicolee]

Answer to Question 1

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. Because test scores are for two independent groups, this is an independent sample t test.
Rationale 2: A paired or dependent sample t test usually has two measures on one groupa 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.
Global Rationale:

Answer to Question 2

2
Rationale 1: Type I errors can only occur when the researcher does reject the null hypothesis and in actuality there is no difference between the group. Type I errors are considered false positives.
Rationale 2: A type II error is a false negative.
Rationale 3: Standard errors of the mean are considered in population statistics only when confidence intervals are calculated.
Rationale 4: There is no type III error.
Global Rationale: