What area of the United States has the least amount of daylight, on average? Having grown up in western Pennsylvania, co-author Sincich wonders if it is his hometown of Sharon, PA. Data on the number of minutes of daylight per day in Sharon, PA, for 12 randomly selected days (one each month) in a recent year were obtained from the Naval Oceanography Portal Web site (aa.usno.navy.mil/USNO/astronomical applications/ data- services). The data are listed in the table. Descriptive statistics and a 95% confidence interval for the mean are produced in the SPSS printout in the next column.
a. Locate the confidence interval on the printout and give the value of the confidence coefficient.
b. Use the descriptive statistics on the printout to calculate the 95% confidence interval. Be sure your answer agrees with the interval shown on the printout.

c. Practically interpret the confidence interval.
d. Comment on the method of sampling. Do you think the sample is representative of the target population?
SPSS Output for Exercise 7.43

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591 618 704 831 896 909 865 839 748 672 583 565 Statistic Std. Error DAYLIGHT Mean 735.08 37.402 95% Confidence Interval Lower Bound 652.76 for Mean Upper Bound 817.40 5% Trimmed Mean 734.87 Median 726.00 Variance 16786.992 Std. Devialion 129.565 Minimum 565 Maximum 909 Range 344 Interquartile Range 261 Skewness 016 .637 Kurtosis -1.752 1.232