MidtermExams_Spring2021_Part2.pdf

PH 661 Biostatistics II – Spring 2021

Midterm

Instructor: Charles Edeki

Student Name: Date:

Solve the problem (4 points each)

18.

A researcher is interested in the toxicity of cigarette smoking in humans. One variable measure

that he decides to investigate involves measuring the pH of the urine from smokers to see if there

is an increase in toxicity. In to carry out a statistical test, the researcher collects a SRS of

61 current smokers from a population with a known standard deviation of 0.8.

A) If the researcher wants to be 95% confident about his estimate, calculate the margin of error

based on the above information.

B) Carry out the same calculation above, but assuming the researcher wishes to be “virtually

certain” about his estimate. (Use Z=3.0)

C) Compare the margin of errors calculated above.

21.

An investigator wants to determine if a new program aimed at reducing the overall number of

pregnancies in a highly populated area is effective (reducing average births below 6 per

household). In to carry out the investigation, the investigator conducts a SRS of 189

participants in the program and finds the average number of births is 4.7 with a sample standard

deviation of 0.9 births. Construct a 95% confidence interval for the average number of births per

household in this study. Provide a correct interpretation of your interval.

22.

Suppose a researcher is interested in the effectiveness of a new drug that is intended to naturally

increase hours of sleep for elderly patients experiencing insomnia. Suppose he collects

information from a group of 64 patients, and calculates a σ=.8 and a sample average of 6.4 hours

of sleep. Is there sufficient evidence to reject the null hypothesis that his treatment is ineffective

at increasing hours of sleep above 5 hours with 95% confidence?

23.

A research team wants to investigate the impact of increased sun exposure to a decrease in

depression. In to do so, the team gathers a SRS of 124 individuals with a sample average

score on the Geriatric Depression Scale (GDS) of 7.5 from a population with σ=.4 after

consistent sun exposure above 7 hours a day. Assume a clinical diagnosis for depression can only

be given with a GDS score of 9.

A) Is the team correct in their hypothesis?

B) State and interpret your results.

Multiple Choice (4 points each question)

24.

When the mean and median are equal, what can be said about the shape of the distribution?

A) More information should be presented if assumptions pertaining to the shape of the

distribution are to be made.

B) When the mean is equal to the median, the shape of the distribution tends to be slightly

skewed right.

C) When the mean is equal to the median, the shape of the distribution tends to be slightly

skewed left.

D) When the mean is equal to the median, the shape of the distribution can be assumed relatively

symmetrical.

25.

Removing a positive outlier from a dataset would do all but the following?

A) Reduce the average

B) Reduce the median

C) Increase the spread

D) Decrease the spread

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