Question

Suppose we have collected times, in minutes, that it takes volunteers to complete a set of pencil and paper mazes. Volunteers are randomly assigned to one of two groups. Group 1 watch a 5 minute video explaining good strategies for completing the mazes. Group 2 watch a 5 minute video of other people successfully completing the mazes, but with no explanation given.

Researchers are interested in testing against the null hypothesis that there is no difference in population mean times that it takes people to complete mazes after watching either type of video.

There are the summary statistics after collecting data. Note that the sample sizes differ, because some subjects did not follow instructions correctly and so they were not included in the analysis.

x₁ = 13, x₂ = 8.66
s₁ = 8.24, s₂ = 7.02
n₁ = 48, n₂ = 55

a. Is this an experimental or observational study?

b. What are the predictor and response variables, and are they categorical or quantitative?

c. How should the null hypothesis be written?

Calculate the standard error of x₁ - x₂:
Calculate the approximate 95% CI for μ₁ - μ₂: ___ to ___

The result of the hypothesis test is:
- We do not have evidence that there is a difference in population means, because the null value is inside the 95% CI.
- We do not have evidence that there is a difference in population means, because the null value is outside the 95% CI.    
- We have evidence that there is a difference in population means, because the null value is inside the 95% CI.
- We have evidence that there is a difference in population means, because the null value is outside the 95% CI.

d. What kind of error is it *possible* that we have made?

Answer 1