When testing for a difference between the means of a treatment group and a group given a placebo, the following Excel display is obtained. Using a 0.05 significance level, is there sufficient evidence to support the claim that the treatment group (Variable 1) comes from a population with a mean that is less than the mean for the placebo population? Explain.

Transcribed Image Text:

1 z-Test: Two Sample for Means Variable 1 Variable 2 4 Mean 5 Known variance 6 Observations 7 Hypothesized mean difference 152.0739 154.9669 438.4388 239.1461 50 50 9 P(Z< z) one-tail 10 z Critical one-tail 11 P(Z