Question

For all hypothesis tests, be sure to include information for all 7 steps. For any two-sample or paired t-tests that you perform, in Step 6, show the decision rule based on BOTH the critical value and the p-value. Use the online app for the t-distribution to compute your p-values.

1. Cortisol level determinations were made on two samples of women at childbirth. Group 1 subjects underwent emergency cesarean section following induced labor. Group 2 subjects delivered by either cesarean section or the vaginal route following spontaneous labor. The samples sizes, mean cortisol levels, and standard deviations were as follows:

Sample	N	Mean	St. Dev
Group 1	10	435	61
Group 2	12	645	88

Assume that the cortisol levels are approximately normally distributed in each group.

1. Do these data provide sufficient evidence to indicate a difference in the mean cortisol levels in the populations represented? Perform a hypothesis test at the 5% significance level.

2. Construct and interpret a 95% confidence interval for the difference in the population means.

Answer 1

P value and statistical significance:   The two-tailed P value is less than 0.0001   By conventional criteria, this difference is considered to be extremely statistically significant. Confidence interval:   The mean of Group One minus Group Two equals -210.00   95% confidence interval of this difference: From -278.80 to -141.20 Intermediate values used in calculations:   t = 6.3670   df = 20   standard error of difference = 32.982