Question

THE LAST PERSON GOT IT WRONG AND EXPLAINED WRONG

Child Health and Development Studies (CHDS) has been collecting data about expectant mothers in Oakland, CA since 1959. One of the measurements taken by CHDS is the weight increase (in pounds) for expectant mothers in the second trimester.

In a fictitious study, suppose that CHDS finds the average weight increase in the second trimester is 14 pounds. Suppose also that, in 2015, a random sample of 43 expectant mothers have mean weight increase of 16.2 pounds in the second trimester, with a standard deviation of 5.7 pounds.

A hypothesis test is done to see if there is evidence that weight increase in the second trimester is greater than 14 pounds.

Find the p-value for the hypothesis test.  

The p-value should be rounded to 4 decimal places.

2.

A medical researcher is studying the effects of a drug on blood pressure. Subjects in the study have their blood pressure taken at the beginning of the study. After being on the medication for 4 weeks, their blood pressure is taken again. The change in blood pressure is recorded and used in doing the hypothesis test.

Change: Final Blood Pressure - Initial Blood Pressure

The researcher wants to know if there is evidence that the drug reduces blood pressure. At the end of 4 weeks, 31 subjects in the study had an average change in blood pressure of -2.7 with a standard deviation of 5.3.

Find the p-value for the hypothesis test.

Your answer should be rounded to 4 decimal places.

3.

Dean Halverson recently read that full-time college students study 20 hours each week. She decides to do a study at her university to see if there is evidence to show that this is not true at her university. A random sample of 31 students were asked to keep a diary of their activities over a period of several weeks. It was found that the average number of hours that the 31 students studied each week was 18.9 hours. The sample standard deviation of 3.7 hours.

Find the p-value.  

The p-value should be rounded to 4-decimal places.

Answer 1

(a) To perform the right-tail hypothesis test, we use the six-step method. Step 1: The null and altenative hypotheses are as follows. Ho 14 (The populati on mean is equal to 14) Ha 14 (The population mean is greater than 14) Step 2: The Deci sion Rule If the test statistic is t>00542 = 1.681952 We reject the null hypothesis Ho Otherwise, we do not reject the nul1 hypothesis Hp. We have selected a sample of n 43. We decide to use a= 0.05 is unknown, we use the t - distributi on and the - test stati stic. Step3: Because Step4: For a given sample size, n, the test stati sti ct follows at di stribution with n-1 degrees of freedom The critical values of the t distribution with 43-142 degrees of freedom. The table of t test is obtained by using the Excel2010 function = tinv(probability,degrees of freedom) tinv(0.05,42) =1.681952 0.05.42 = 1.681952 Step5: The summary stati stics: The sample mean is X = 16.2 pounds. The sample standard deviation is closest to s= 5.7 pounds The sample size is n 43. The -test stati stic is s 16.2 14 5.7 43 2.2 5.7 6.557439 2.2 0.869242 = 2.530941 t2.530941 Step6: The P-value approach: P-value P(t to) 1 - P (t <) 1-P(t <2.530941) 1-0.992395 0.007605 P-value0.007605 a0.05 We reject the null hypothesis Ho Step7: Conclusion: Since, the test stati stic is 2.53094100542 1.681952 We reject the null hypothesis Ho There is sufficient evi dence to conclude that the mean weight increase in the second trimester is greater than 14 pounds at the 5% level of significance.