Question

Cindy has two groups. She randomly assigns subjects to her two groups. She has one group spend 10 minutes writing about a sad time in their life. She has the other group write about a happy time in their life. Then she gives both groups a persuasive message about bicycle helmets and measures their attitude about bicycle helmets. She predicts that the sad group will be more persuaded than the happy group.

Tell me the if the hypothesis stated is directional or non-directional. Next, tell me what specific t-test is needed and why.

Answer 1

Let mu1 be true average score for sad group and mu2 be true average score for happy group.

Claim: The sad group will be more persuaded than the happy group

Null hypothesis, H0: mu1=mu2 vs. Alternative hypothesis, H1: mu1>mu2 (claim)

Hence the hypothesis is directional i.e. right tailed test.

Since we take two independent sample from two groups and assume that two samples come from two independent normal populations so we apply 2 sample t test.

Now we check whether two population variances are equal or not through F test.

If F test is insignificant then we apply 2 sample t test with equal variances. Otherwise we apply 2 sample t test with unequal variances.