STAT 600 – Assignment #1 46 points - (DUE 1/21/15 by midnight – Submit to D2L)
This assignment is due January 24th by noon and should be submitted via the Assignment 1 dropbox on D2L. However, please be prepared to discuss questions 1 – 4 under Part 2 of the assignment in class on Wednesday, January 22nd.
Part 1 – Lecture Review
First review the narrated (or non-narrated) lectures linked to STAT 600 website entitled:
Part 2 – Assigned Problems
Type your answers the questions below on this document or in a separate document. Be as explicit as possible addressing how you carry out the study and variables would be measured. Again be prepared to discuss questions 1, 2, and 3 in class on Wednesday but your typed up response to these questions will be submitted with your answers to the remaining questions.
1. Researchers wish to design a study to examine the potential of effects of a cranberry dietary supplement on muscle pain associated with routine weight lifting/strength training. They also interested in the potential effects this supplement may have on flexibility. You have 100 volunteers (50 men, 50 women) who are in good health and are currently exercising about 3 times a week on average. Discuss how you would design a study to examine the potential benefits of cranberry in terms pain and flexibility. (6 pts.)
2. Discuss how you would conduct a field study to determine factors that could potentially influence whether or not a duck nest will be “successful”, i.e. the eggs will hatch and not be eaten by predators. (5 pts.)
3. Discuss how you would conduct a study to determine the potential risk for developing cervical cancer later in life associated with having a child before the age of 25. (5 pts.)
4. A researcher wishes to determine what changes there were, if any, in the population of fish following the dredging of East Lake Winona (the big lake). How might you conduct a study to examine these potential changes? What variables would you measure? Using these variables how might you measure “change”? (5 pts.)
More short answer questions pertaining to study design and conclusions reached from studies …
5. A study found that individuals who lived in homes with more than two bathrooms tended to have higher blood pressures than individuals who lived in homes with two or fewer bathrooms.
(a) Can cause-and-effect be inferred from this? Explain your answer. (3 pts.)
(b) What confounding variables may be responsible for the difference? (3 pts.)
6. A researcher performed a comparative experiment on laboratory rats. Rats were assigned to Group 1 haphazardly by pulling them out of the cage without thinking about which one to select. Should others question the claim that this was a good as randomized experiment? (3 pts.)
7. In 1930 an experiment was conducted on 20,000 school children in England. Teachers were responsible for randomly assigning their students to a treatment group – to receive ¾ pint of milk each day – or to a control group – to receive no milk supplement. Weights and heights were measured before and after the four-month experiment. The study found that children receiving milk gained more weight during the study period. On further investigation, it was found that the controls were heavier and taller than the treatment group before the milk treatment began (more so than could be attributed to chance variation alone). What is the likely explanation and the implication concerning the validity of the experiment? (3 pts.)
8. An except taken from “Lactation suppression: a pilot study” published in the Australian Journal of Advanced Nursing (1986) is as follows:
“The first method (experimental group) was based on a new approach which claimed that post-partum breast discomfort in non-breastfeeding women would be reduced if milk was extracted from the breasts. The second approach (hospital policy) involved adhering to the normal hospital methods. … Non-breastfeeding women admitted to Ward A were assigned to the experimental group (n = 95) and non-breastfeeding women admitted to Ward B acted as the control group or hospital policy group (n = 57). … Three times daily, participants entered details on the questionnaire relating to self-assessment of pain, use of analgesia and methods employed in suppressing lactation.”
Describe any design problems that are evident. Also discuss biases or confounding that might have arisen from any design deficiencies. (5 pts.)
9. An experiment was carried out to measure the effect of growth hormone on girls affected by a growth disorder called Turner’s syndrome. All 34 girls in the study were given the growth hormone. Their heights were measured at the time the hormone was first administered and again one year later. What are some problems with a study conducted in this way? (2 pts.)
10. A researcher wishes to determine if the pH levels differ between the top and bottom of a tank of hand lotion during the manufacturing process. To do so the research collects 20 samples of lotion from the “top” of a tank and 20 samples of lotion from the “bottom” of a tank. Suppose that the difference in the mean pH levels was found to be .5 on the pH scale. Because the difference between these means was not 0, can conclude that the pH levels of the lotion do indeed differ between the top and bottom of the tank during the manufacturing? Explain why or why we can’t reach this conclusion. You can assume the samples were drawn perfectly randomly and they were uncontaminated. (5 pts.)