Note for hypothesis tests: You must show: the null and alternative, the p-value or test statistic, the rejection region or inequality used to make the decision, the decision, the interpretation IN TERMS OF THE GIVEN SITUATION. Use a significance level of 5% in all problems. You may use either the p-value method or the rejection region method. This is up to you.

1. a) A random sample of prices of 18 sleeping bags had a mean price of $83.75 with a standard deviation of $31.82. Find a 99% confidence interval for the mean price of all sleeping bags.

b) Interpret your interval in the context of the problem.

c) What is the margin of error for your interval?

2. The following is a sample several patient's weights at a medical practice (lbs)

142	212	180	182	190
126	220	145	160	134

Find each of the following.

The mean:

The median:

The third quartile:

The standard deviation:

The variance:

3. Privacy is a concern for many users of the internet. One survey showed that 42% of internet users are somewhat concerned about confidentiality of their email. A random sample of 7 people is taken. Use this information to find the following.

a) The probability that all people sampled are somewhat concerned about confidentiality of their email.

b) The probability that 4 or fewer people sampled are somewhat concerned about confidentiality of their email.

c) The probability that exactly 7 people sampled are somewhat concerned about confidentiality of their email.

d) The probability that more than 6 people sampled are somewhat concerned about confidentiality of their email.

e) The probability that between 2 and 5 of the people sampled are somewhat concerned about confidentiality of their email.

4. There are 3 defective hard drives out of 10 rolls of hard drives in a box. Two hard drives are to be selected for testing, one at a time, without replacement.

a) What is the probability that first HD selected is defective and the second HD selected is NOT defective?

b) What is the probability both are NOT defective?

c) What is the probability at least one is NOT defective?

5. The owner of Bun'N'Run Hamburger wishes to compare the number of daily sales at two locations. The mean number of daily sales for 8 randomly selected days at the North-side was 72 with a standard deviation of 13.50. For 9 randomly selected days at the South-side location the mean number of daily sales was 85 with a standard deviation of 14.25. Assume the distributions of daily sales for both locations are normal with equal amounts of variation. At 5% significance level, is the number of daily sales of hamburgers at North-side significantly less than at South-side location?

6. Assume that the salaries of elementary school teachers in the US are normally distributed with a mean of $52,000 and a standard deviation of $6,075.

a) What percentage of elementary school teachers have a salary of more than $50,000?

b) If 1100 teachers are selected, how many would you expect, approximately, to have a salary of less than $48,000?

c) What is the 67th percentile of salaries?

7. According the USDA, 44.2% of males between 20 and 39 years old consume the minimum daily requirement of calcium. After an aggressive "Got Milk?" campaign, the USDA conducts a survey of 65 randomly selected males between the ages of 20 and 39 and finds that 47 of them consume the recommended daily allowance of calcium. Is there evidence to conclude that the percentage of males between the ages of 20 and 39 who consume the minimum recommended daily allowance of calcium has increased?

8. Stargell Research Associates conducted a study of the radio listening habits of men and women. One facet of the study involved the listening time. In random sample of 10 women, the mean listening time was 34.1 minutes per day with a standard deviation of 12.3 minutes per day. In an independent sample of 10 men, the mean listening time was 25.6 minutes per day with a standard deviation of 9.3 minutes per day. Assume the distributions of listening times for both men and women are normal. At 5% significance level, is there enough evidence to believe that there is more variation in the listening time for women than for men?

9. For years, a large discount store has used independent lines to check out customers. Historically, the standard deviation of waiting times is 10 minutes. The manager tried a new, single-line procedure. A random sample of 32 customers using this method had a standard deviation of 9.5 minutes in waiting time. Assuming waiting times are normal, test the claim that the st dev of the waiting times are reduced by the new procedure using a significance level of 5%.

10. A company orders the memory for their devices from two suppliers. Supplier A supplies 82% of the memory while supplier B supplies the remainder. Previous testing has shown that 1.1% of Supplier A's memory is defective and 1.9% of Supplier B's memory is defective. A randomly selected memory chip is defective. Find the probability it came from supplier B.