Constructing Confidence Intervals

1. In a clinical trial of a new drug, 23 subjects experience headaches among the 216 subjects treated with the new drug. Construct a 99% confidence interval estimate for the proportion of treated subjects who experience headaches.

Margin of Error:

Confidence Interval:

Interpretation:

2. In a survey of 3106 adults aged 57 through 85 years, it was found that 80.4% of them used at least one prescription medication. Construct a 90% confidence interval estimate of adults aged 57 through 85 who use at least one prescription medication.

Margin of Error:

Confidence Interval:

Interpretation:

3. In a program designed to help patients stop smoking, 202 patients were given sustained care, and 83.2% of them were no longer smoking after one month. Among 207 patients given standard care, 63.8% were no longer smoking after one month. Using a 95% confidence level, construct two confidence interval estimates of the percentages of success.

Margin of Error:

Confidence Interval:

Interpretation:

Margin of Error:

Confidence Interval:

Interpretation:

4. Construct a 90% confidence interval for randomly selected weights of newborn girls: n = 282, = 32.9 hg, s = 7.8 hg.

Margin of Error:

Confidence Interval:

Interpretation:

5. A data set includes 108 body temperatures of healthy adult humans having a mean of 98.2°F and a standard deviation of 0.64°F. Construct a 99% confidence interval estimate of the mean body temperature of all healthy humans.

Margin of Error:

Confidence Interval:

Interpretation:

6. Construct two confidence interval estimates for the mean pulse rate of adult females and adult males. Use a 90% confidence level.

Males

Females

n =

40

40

=

67.2

75.7

s =

12.27

13.41

Margin of Error:

Confidence Interval:

Interpretation:

Margin of Error:

Confidence Interval:

Interpretation:

7. A simple random sample from a population with normal distribution of 100 body temperatures has = 98.3°F and s = 0.64°F. Construct a 95% confidence interval estimate of the standard deviation of body temperature of all healthy humans.