A consumer psychologist asked to test a claim by a swimming school that its instructors could teach the average seven-year-old to swim across an Olympic-sized pool in less than 2 minutes. The psychologist arranged for eight randomly selected seven-year-old children to take lessons at the school and recorded how long it took each child to swim across a pool at the end of the lessons. The times (in seconds) were 60, 120, 110, 80, 70, 90, 100, and 130. What conclusion would the psychologist draw following a t test for a single sample using 120 seconds as the "known" population mean and the .05 significance level?
First of all, what type of t test would you use here? You are comparing your test group against the "known" population.
Next, using the results I have provided below, tell me if this study is significant and why. (You don't have to work anything out; just analyze the study's results that are presented.)
df = 7
Cutoff t score needed = -1.895 (p < .05, 1-tailed)
t = 2.88