1. You intend to estimate a population mean with a confidence interval. You believe the population to have a normal distribution. Your sample size is 30. Find the critical value that corresponds to a confidence level of 80%. (Report answer accurate to three decimal places with appropriate rounding.)

ta/2 = ±

2. If n=130 and ˆp (p-hat) =0.69, find the margin of error at a 90% confidence level. Give your answer to three decimals

3. Out of 500 people sampled, 270 had kids. Based on this, construct a 99% confidence interval for the true population proportion of people with kids. Give your answers as decimals, to three places

< p <

4. Assume that a sample is used to estimate a population proportion p. Find the 99.5% confidence interval for a sample of size 307 with 221 successes. Enter your answer as a tri-linear inequality using decimals (not percents) accurate to three decimal places.

< p <

The answer should be obtained without any preliminary rounding. However, the critical value may be rounded to 3 decimal places.

5. We wish to estimate what percent of adult residents in a certain county are parents. Out of 600 adult residents sampled, 300 had kids. Based on this, construct a 90% confidence interval for the proportion p of adult residents who are parents in this county. Give your answers as decimals, to three places.

< p <

6. Assume that a sample is used to estimate a population proportion p. Find the 99.5% confidence interval for a sample of size 174 with 155 successes. Enter your answer as an open-interval (i.e., parentheses) using decimals (not percents) accurate to three decimal places.

99.5% C.I. =

The answer should be obtained without any preliminary rounding. However, the critical value may be rounded to 3 decimal places.

7. For a confidence level of 98% with a sample size of 19, find the critical t value.

8. If n=28, ¯x(x-bar)=48, and s=2, find the margin of error at a 90% confidence level. Give your answer to two decimal places.

9. In a survey, 21 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $49 and standard deviation of $3. Find the margin of error at a 95% confidence level. Give your answer to two decimal places.

10. If n=16, ¯x(x-bar)=45, and s=13, construct a confidence interval at a 95% confidence level. Assume the data came from a normally distributed population. Give your answers to one decimal place.

< μ <

1. You intend to estimate a population mean with a confidence inter...