Duration of daylight in western Pennsylvania. Refer to the Naval Oceanography Portal data on number of minutes of daylight per day in Sharon, PA, Exercise 7.43 (p. 363). An estimate of the mean number of minutes of daylight per day was obtained using data collected for 12 randomly selected LO6 days (one each month) in a recent year.

a. Determine the number of days that need to be sampled in order to estimate the desired mean to within 45 minutes of its true value with 95% confidence.

b. Based on your answer, part

a, develop a sampling plan that will likely result in a random sample that is representative of the population.

c. Go to the Web site, http://aa.usno.navy.mil/USNO/

astronomical-applications/data-services, and collect the data for Sharon, PA using your sampling plan.

d. Use the data, part

c, to construct a 95% confidence interval for the desired mean. Does your interval have the desired width?