How many subjects participated in an independent-samples t-test if a researcher reports, t (20) = 3.68, alpha = .05, two-tail?

Rhino viruses typically cause common colds. In a test of the effectiveness of echinacea, 34 of the 39 subjects treated with echinacea developed rhinovirus infections. In a placebo group, 98 of the 115 subjects developed rhinovirus infections. Use a 0.05 significance level to test the claim that echinacea has an effect on rhinovirus infections. Complete parts (a) through (c) below. Identify the test statistic:Z= ___?____ Identify the P-Value: _______State the conclusion about the null hypothesis, as well as the final conclusion that addresses the original claim. _________Identify the confidence interval limits for the appropriate confidence interval.__?____ < P1-P2 < __?____

Don't need help with first part of a, got that figured out.   Recall that small effects may be statistically significant if the samples are large. A study of small-business failures looked at 147 food-and-drink businesses. Of these, 103 were headed by men and 44 were headed by women. During a three-year period, 15 of the men's businesses and 6 of the women's businesses failed. (a) Find the proportions of failures for businesses headed by men (sample 1) and businesses headed by women (sample 2). These sample proportions are quite close to each other. p̂men =  p̂women =  Give the P-value for the z test of the hypothesis that the same proportion of women's and men's businesses fail. (Use the two-sided alternative.) The test is very far from being significant. (Round your test statistic to two decimal places and your P-value to four decimal places.) z =  P-value =  (b) Now suppose that the same sample proportions came from a sample of 30 times as large. That is, 180 out of…

The leader of two postpartum women’s support groups is interested in the depression levels of the women in her groups. She administers the Center for Epidemiologic Studies Depression Scale (CES-D) screening test to the members of her groups. The CES-D is a 20-question self-test that measures depressive feelings and behaviors during the previous week. The mean depression level from the screening test for the 10 women in the first group is μ₁ = 16; the mean depression level for the 14 women in the second group is μ₂ = 10. Without calculating the weighted mean for the combined group, you know that the weighted mean is: