Question

1. You have been hired by Ford Motor Company to do market research and you must estimate the percentage of households in which a vehicle is owned. How many households must you survey if you want to be 94% confident that your sample percentage has a margin of error within 0.03?

                                                                                                                                                              (5)

2. The monthly utility bills in a city are normally distributed with a mean of $100 and a standard deviation of $1 If 300 utility bills are randomly selected, about how many would you expect to be more than $90?                                                                                                                             (6)

3. Two percent of hair dryers produced in a certain plant are defective. What is the probability that of 10,000 randomly selected hair dryers, exactly 225 are defective?                                 (14)
4. Based on a sample of 43, a 95% confidence interval for the mean score of all students on an aptitude test is from 62 to 69.8. Find the margin of error.                                                   (2)

5. The incomes of trainees at a local mill are normally distributed with a mean of $1100 and a standard deviation of $150. Find the percent having an income between $1100 and $1350. (6)

6. Use the continuity correction and describe the region of the normal curve that corresponds to the indicated binomial probability:                                                                                              (4)

1. The probability of no less than 53 correct answers.

2. The probability of fewer than 52 Democrats.

Answer 1

Here, the statistic is , which is the sample proportion that was taken from the population. If is given and the confidence interval % is given then the margin of error ME=z*√[(1-)/n]