Quiz One ID:
Professor Colson
Summer 2005
1.) A study conducted to assess whether taking supplements of zinc might help certain women deliver larger babies � particularly those women who are thin when they get pregnant. Half of the women in the study took prenatal vitamins containing 25 mg of zinc. The other group received the same vitamins but without zinc. The results were reported in JAMA (Journal of the American Medical Association). The study compared average birth weight, premature delivery rates, and Caesarean delivery rates. There was no significant difference in the Caesarean delivery rates between the two groups.
a.) What type of study is this and why?
Experimental study because there are two groups under study � the ones that take zinc and those that don�t.
b.) Name the two hypothesis of this study.
Ho: zinc doesn�t help and/or both groups have the same size babies, etc.
H1: zinc does help and there is a difference between the two groups of women.
c.) Would the p-value for this study be greater than, cannot tell, or less than ? = 0.05 and why?
Greater than 0.05 because we still accept Ho.
2.) A college president wants to take a survey of 2250 students in the school. Each student has an identification number on the administrative computer. For each of the following descriptions, give the name of the sampling technique and the total sample size (if the sample size cannot be determined, write �cannot be determined�):
a.) Students listed alphabetically and this list was broken down into 50 sections of 45 students each. The administration selected a random number between 1 and 45, obtaining 33. Then they selected the 33rd student from each of the 50 sections.
50 students / stratified sampling
b.) The schools constructs a list of all the possible undergraduate majors and takes a simple random sample of six majors, interviewing all the students in those six selected majors.
Cannot tell / cluster sampling.
3.) A New Zealand study that followed 1000 children through age 18 has found that those who were breast-fed as children fared better in school, both in teacher ratings and in performance on standardized tests. The authors of the study conjecture that fatty acids found in breast milk, but not in formula, may boost brain development.
a.) What are the response variables?
Teacher ratings and standardized tests
b.) What are the explanatory variables?
Breast-fed children
c.) Suppose we test with the following hypothesis:
Ho: There is no association between duration of breastfeeding and IQ.
H1: There is an association between duration of breastfeeding and IQ.
The results were statistically significant at the 10% level. Select from each of the following:
i.) The chance of a Type II error is 0.10 True False Can�t Tell
ii.) The null hypothesis was accepted. True False Can�t Tell
iii.) The p-value was smaller than 0.10 True False Can�t Tell
iv.) The p-value was smaller than 0.01 True False Can�t Tell
4.) Suppose that the p-value for a statistical test is found to be 0.04 and the significance level was 0.05. Determine whether each of the following statements is true or false. If false, explain why.
a.) The chance that Ho is true is 0.04.
False
b.) The decision was to reject Ho.
True
c.) The results are statistically significant at 0.05.
True
d.) In hypothesis testing, if the decision is to accept Ho, a Type II error could have been made.
True
e.) In hypothesis testing, if the null hypothesis is true, a Type I error could have been made.
True
f.) In cluster sampling, if all the clusters contain the same number of units, then cluster sampling is the same as simple random sampling.
False
g.) In 1-in-3 systematic sampling, you can obtain a sample with three consecutive units of the population.
False