In a random sample of 500 people aged 20-24, 22 were smokers. In a random sample of 450 people aged 25-29, 14 were smokers.
Do the data provide sufficient evidence to conclude that the proportion of smokers in the 20-24 age group is different from the proportion of smokers in the 25-29 age group? Use a significance level of 0.01.
Q. 2Suppose that you know the area under the standard normal curve to the right of 2 and the area under the standard normal curve to the right of 1.
Without further consulting a table of areas, how could you find the area under the standard normal curve between 1 and 2? Explain your reasoning.
Q. 3A medical researcher obtains a sample of adults suffering from diabetes. She randomly assigns 84 people to a treatment group and 84 to a placebo group.
The treatment group receives a medication over a period of three months and the placebo group receives a placebo over the same time frame. At the end of three months the patients' symptoms are evaluated.
A) observational study B) experiment
Q. 4Many firms use on-the-job training to teach their employees new software.
Suppose you work in the personnel department of a firm that just finished training a group of its employees in new software, and you have been requested to review the performance of one of the trainees on the final test that was given to all trainees. The mean and standard deviation of the test scores are 82 and 2, respectively, and the distribution of scores is mound-shaped and symmetric. Suppose the trainee in question received a score of 77. Compute the trainee's z-score.
A) z = -0.91 B) z = 2.5 C) z = -2.50 D) z = 0.91
Q. 5A farmer wishes to test the effects of a new fertilizer on her corn yield. She has four equal-sized plots of land-- one with sandy soil, one with rocky soil, one with clay-rich soil, and one with average soil.
She divides each of the four plots into three equal-sized portions and randomly labels them A, B, and C. The four A portions of land are treated with her old fertilizer. The four B portions are treated with the new fertilizer, and the four C's are treated with no fertilizer. At harvest time, the corn yield is recorded for each section of land. How many levels does the treatment have in this experiment?
A) 1 (corn yield) B) 12 (sections of land)
C) 4 (rocky, sandy, clay, or average soil) D) 3 (old, new, or no fertilizer)
Q. 6A new phone system was installed last year to help reduce the expense of personal calls that were being made by employees.
Before the new system was installed, the amount being spent on personal calls followed a normal distribution with an average of 900 per month and a standard deviation of 50 per month. Refer to such expenses as PCE's (personal call expenses). Using the distribution above, what is the probability that a randomly selected month had a PCE of between 775.00 and 990.00?
A) 0.9999 B) 0.0421 C) 0.9579 D) 0.0001
Q. 7A mayoral election race is tightly contested. In a random sample of 1600 likely voters, 832 said that they were planning to vote for the current mayor. Based on this sample, would you claim that the mayor will win a majority of the votes? Explain.
What will be an ideal response?
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