# Narrow Distribution

1 . A random sample of 34 eight ounce servings of different juice drinks has a mean of 95.8 calories and a standard deviation of 44.3 calories. The 90% confidence interval is______ and the 95% confidence interval is ______. which one is wider?

2. People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90% confidence. Initial survey results indicate that o=19.3 books. A 90% confidence level requires______ subjects? Round to the nearest whole number.

3. A doctor wants to estimate the cholesterol of all 20-29 year old females. How many subjects are needed to estimate the cholesterol within 3 points with 99% confidence assuming o=13.3? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required?
99% confidence level requires_____ subjects
90% confidence level requires _____ subjects
How does the decrease in confidence level affect the sample size?

4. Construct the confidence interval for the population mean u using (a) a t-distribution. (b) If you had incorrectly used a normal distribution, which interval would be wider?
a._______
b._____

5 (a) In a random sample of 10 adults the mean waste generated per person per day was 4.45 pounds and the standard deviation was 1.31 pounds. The 90% confidence interval is (__,__).

(b) What if the sample size was 400 adults. The 90% confidence level would be (__,__)
Was normal distribution or t-distribution used? And is (a) or (b) more narrow?

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