STAT 121: Writing Assignment 1 Confidence Intervals

Directions: Read the following article and answer each question completely but concisely. Be sure to save a copy of your work, and see the syllabus for submission details. (The spacing between the questions is not necessarily an indication of the expected response length.)

Journal March 26, 2010

Resting Heart Rates of American Adults

A normal resting heart rate for adults ranges from 60 to 100 beats a minute," reports Dr. Edward Laskowski of the Mayo Clinic. Lower resting heart rates are generally associated with higher cardiovascular fitness. With the marked increase in obesity in America, there is rising concern that the average resting heart rate of American adults is trending towards the higher end of the accepted range. A recent study conducted by the Statistical Health Association of America validates this concern. Results were based on a sample of 1587 American adults (ages 18 and older). The mean resting heart rate from this sample was calculated at 87 beats per minute (bpm). The study concludes, with 95% confidence, that the true mean resting heart rate of American adults is in the interval (80, 94).

1. (1 point) What is the population that the confidence interval in the article is making an inference about? Be specific.

2. (1 point) What is the parameter of interest for the confidence interval in context?

3. (2 points) Give the confidence interval as reported in the article. Is the reported interval in the form of an interval or is it in the form of estimate ± margin of error? If it is not in interval form, give it in interval form.

4. (2 points) What confidence level is associated with the given interval? Is the choice of confidence level reasonable? Why or why not?

5. (2 points) Interpret the confidence LEVEL given in your previous answer in your previous answer in the context of the problem.

6. (2 points) How was the sample collected? Does this allow us to infer things about the population? If the article does not state how it was collected, how SHOULD it have been collected?

7. (3 points) Interpret your calculated interval in context. Make sure to include all three parts of a confidence interval interpretation.