Honors IS Lab- the t-test

Today in lab I introduced you to the t-test, showed you how to conduct a t-test on Excel to compute the p-value, and finally how to use the p-value to help you correctly evaluate your hypotheses. Although I think that people were getting a hang of what was going on by the end of lab, my experience tells me that unless you sit down and think deeply about the material before next week that you will be unlikely to master the material. As I mentioned today, there will be a midterm testing your knowledge of the statistical tests. I think it would be helpful for you to get some practice answering the types of questions that you will be required to answer on the exam.

1. When do you use a t-test to help test your hypotheses?

2. Why do you use a t-test to help test your hypotheses?

3. Give an example of a question that needs to be answered using a two-tailed, paired t- test. (be sure to state the Ha and Ho and how you will collect the data)

4. Give an example of a question that needs to be answered using a one-tailed, unpaired t-test. (be sure to state the Ha and Ho and how you will collect the data)

5. Scientists is interested in knowing whether adding insecticides to a cotton field increases cotton yield. In several fields they spray insecticide on the fields and in several fields they do not add insecticides (the control plots).

Q. What statistical test should the scientists do to help answer their question?

6. Scientists are interested in knowing whether there is a difference in the male and the female students with the top GPAs in a univesity. They collected their data by examining the GPAs of the top male and female students at Texas Tech, Texas A&M, UT, and 12 other universities in Texas.

Q. What statistical test should the scientists do to help answer their question?

7. John, a new third grade teacher, noticed that his male students seemed to need to leave the class the restroom more often than did his female students. He decided to see if male students in his class peed on average more often each week than female students. For four weeks he counted the number of time that each student was excused from class to go the the restroom. What statistical test should John use to analyze his data?

(a) one-tailed, paired t-test
(b) one-tailed, unpaired t-test
(c) two-tailed, paired t-test
(d) two-tailed, paired t-test
(e) John does not need to use statistics to answer his question.

8. A scientist was interested in testing whether the grapefruit diet (eating only grapefruits for three months) or the doughnut diet (eating only doughnuts for three months( resulted in greater weight loss. Researchers located 30 volunteers and randomly assigned half of them to each diet. After three months the researchers determined the amount of weight lost by each participant. Here is the data-

weight loss (lbs)

Grapefruit Diet

5
4
3
5
2
1
3
0
5
7
5
3
9
2
4

Doughnut Diet

1
2
2
3
1
4
2
5
1
2
3
1
3
2
1

Follow all of the steps of the hypothesis testing protocol to determine which diet was most effective (make sure you write down all of the steps of the hypothesis testing protocol).