11.3

Express the confidence interval 0.6830.0820.6830.082 in open interval form (i.e., (0.155,0.855)). ______

11.5

We wish to estimate what percent of adult residents in a certain county are parents. Out of 100 adult residents sampled, 76 had kids. Based on this, construct a 95% confidence interval for the proportion p of adult residents who are parents in this county.

Express your answer in tri-inequality form. Give your answers as decimals, to three places.

____< p < _____ Express the same answer using the point estimate and margin of error. Give your answers as decimals, to three places.

p =_____ _______

11.6

A smart phone manufacturer is interested in constructing a 95% confidence interval for the proportion of smart phones that break before the warranty expires. 88 of the 1599 randomly selected smart phones broke before the warranty expired. Round answers to 4 decimal places where possible.

a. With 95% confidence the proportion of all smart phones that break before the warranty expires is between _____and ______

b. If many groups of 1599 randomly selected smart phones are selected, then a different confidence interval would be produced for each group. About ______percent of these confidence intervals will contain the true population proportion of all smart phones that break before the warranty expires and about _________percent will not contain the true population proportion.

11.7

Out of 100 people sampled, 37 preferred Candidate A. Based on this, estimate what proportion of the entire voting population (p) prefers Candidate A.

Use a 99% confidence level, and give your answers as decimals, to three places.

______< p < _____

11.8

Giving a test to a group of students, the grades and gender are summarized below

A B C Total

Male 3 7 16 26

Female 4 10 15 29

Total 7 17 31 55

Let p represent the population proportion of all female students who received a grade of C on this test. Use a 99% confidence interval to estimate p to four decimal places if possible.

_______< p < ____

11.9

Assume that a sample is used to estimate a population proportionp. Find the 95% confidence interval for a sample of size 155 with 13% successes. Enter your answer as anopen-interval(i.e., parentheses) using decimals (not percents) accurate to three decimal places.

C.I. = _______

11.10

Assume that a sample is used to estimate a population proportionp. Find the 98% confidence interval for a sample of size 250 with 54% successes. Enter your answer as a tri-linear inequality using decimals (not percents) accurate to three decimal places.

_____<p< _____

11.11

A political candidate has asked you to conduct a poll to determine what percentage of people support him. If the candidate only wants a 10% margin of error at a 95% confidence level, what size of sample is needed? When finding the z-value, round it to four decimal places. ________

11.12

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately =22.6=22.6. You would like to be 90% confident that your estimate is within 5 of the true population mean. How large of a sample size is required?

n= ______