Test 4A
A survey was done in town of Mechanicsville to estimate the propotion of cars that are red and made by companies based in Japan. A simple random sample of 25 cars from a parking lot at Lee-Davis High School was taken. Which of the following statements is correct?
A different team doing the sampling independently would probably obtain a slight different answer for their sample proportion.
A nutritionist wants to study the effect of storage tine (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively
A specific storage time, a fruit pack, amount of vitamin C
Control groups are used in experiments in order to accomplish which one of the following?
Limit the effects of variables other than the explanatory variable on the outcome
A researcher observes that, on average, the number of divorces in cities with Major League baseball teams is larger than in cities without Major League Baseball teams. Which of the following is the most plausible explanation for this observed association?
The association is due to confounding (Major League teams tend to be in large cities with more people, hence a greater number of divorces)
A survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salaries of women and men. For a random sample of graduates, three variables are to be recorded: sex, starting salary, and area of specialization. Which of the following best describes a conclusion that can be drawn from this study?
Whether there is an association between sex and starting salary among graduates of this nursing school
To test the affect of Music on productivity, a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is
a matched pairs experiment
A maple sugar manufacturer wants to estimate the average trunk diameter of Sugar Maples trees in a large forest. There are too many trees to list them all and take a SRS, so he divides the forest into several hundred 10 meter by 10 meter plots, selects 25 plots at random, and measures the diameter of every Sugar Maple in each one. This is an example of a
cluster sample
We wish to draw a sample of 5 without replacement from a population of 50 households. Suppose the households are number 01, 02,...50, and suppose that the relevant line of the random number table 11362 35692 96237 90842 46843 62719 64049 17823. The households selected are:
households 11 36 23 23 08 42
A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude
nothing, because there is no control group for comparison
A researcher for a consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that will use the company's current detergent formula. The most important reason for this random assignment is that
randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups.
