1. Answers
Proportions Day 1

2. 1. A company that manufactures classroom chairs for high school students claims that the mean breaking strength of the chairs that they make is 300 pounds. One of the chairs collapsed beneath a 220-pound student last week. You wonder whether the manufacturer is exaggerating the breaking strength of the chairs.
a. State the null and alternative hypotheses.
b. Describe a Type I and a Type II error in this situation, and give the consequences of each.
c. Would you recommend a significance level of 0.01, 0.05, or 0.10 for this test? Explain.

3. A random sample of 270 CA lawyers revealed 117 who felt that the ethical standards of most lawyers are high. Does this provide strong evidence for concluding that fewer than 50% of all CA lawyers feel this way.

4. A random sample of 270 CA lawyers revealed 117 who felt that the ethical standards of most lawyers are high. Does this provide strong evidence for concluding that fewer than 50% of all CA lawyers feel this way

5. A telephone company representative estimates that 40% of its customers want call-waiting. To test this hypothesis, she selected a sample of 100 customers and found that 37% had call waiting. At a 1% significance, is her estimate appropriate?

6. A statistician read that at least 77% of the population oppose replacing $1 bills with $1 coins. To see if this claim is valid, the statistician selected a sample of 80 people and found that 55 were opposed to replacing the $1 bills. Test at 1% level.

7. A potato-chip producer has just received a truckload of potatoes from its main supplier. If more than 8% of the potatoes in the shipment have blemishes, the truck will be sent away to get another load from the supplier. A supervisor selects a random sample of 500 potatoes from the truck. An inspection reveals that 47 of the potatoes have blemishes. Carry out a significance test at the 10% significance level. What should the producer conclude?

8. In 2000, a study of HCC algebra students says that 65% of them pass on their first attempt. In 2004, a survey of 450 algebra students reported that 287 passed on their first attempt. Is there sufficient evidence to suggest that the number of students that passed in 2004 is different than in 2000? Let us test at the 10% significance level.