# Confidence Interval for Proportion

On January 7, 2000, the Gallup Organization released the results of a poll comparing the lifestyles of today with previous times. The survey results were based on telephone interviews with a randomly selected national sample of 1,031 adults, 19 years and older.

a. Gallup found that 42 percent of the respondents said that they spend less than three hours watching TV on an average weekday. Based on this finding, calculate a 99 percent confidence interval for the proportion of U.S. adults who say that they spend less than three hours watching TV on an average workday. Do by hand and confirm with Excel.

b. Gallup found that 60 percent said they took part in some form of daily activity to keep physically fit. Find a 95 percent confidence interval for the proportion of U.S. adults who say they take part in some form of daily activity to keep physically fit. Do by hand and confirm with Excel.

Note:Use a 0.05 level of significance where needed.

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#### Solution Summary

This solution is comprised of formula and detailed step-by-step calculation of Confidence Interval for Proportion and provides students with a clear perspective of the underlying concept. The calculations have also been shown in EXCEL for better understanding.