question 7

People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90% confidence? Initial survey results indicate that =15.7 books.

A 90% confidence level requires ____subjects.

(Round up to the nearest whole number asneeded.)

question 8

Let p be the population proportion for the following condition. Find the point estimates for p and q.

In a survey of 1175 adults from countryA, 500 said that they were not confident that the food they eat in country A is safe.

The point estimate forp,

p, is _____

(Round to three decimal places asneeded.)

The point estimate forq,

q, is _____

(Round to three decimal places asneeded.)

question 9

Use technology to construct the confidence intervals for the population variance 2 and the population standard deviation . Assume the sample is taken from a normally distributed population.

c=0.95, s=37, n=19

The confidence interval for the population variance is (___,___)

(Round to two decimal places asneeded.)

The confidence interval for the population standard deviation is (___,___)

(Round to two decimal places asneeded.)

question 10

The monthly incomes for 12 randomly selectedpeople, each with abachelor's degree ineconomics, are shown on the right. Complete parts(a) through(c) below.

Assume the population is normally distributed.

4450.79

4596.15

4366.64

4455.44

4151.46

3727.11

4283.91

4527.65

4407.73

3946.85

4023.79

4221.47

(a) Find the sample mean.

x=

(Round to one decimal place asneeded.)

(b) Find the sample standard deviation.

s=

(Round to one decimal place asneeded.)

(c) Construct a 90% confidence interval for the population mean .

A 90% confidence interval for the population mean is (____,___)

(Round to one decimal place asneeded.)

question 11

A soccer ball manufacturer wants to estimate the mean circumference ofmini-soccer balls within 0.10 inch. Assume the population of circumferences is normally distributed.

(a) Determine the minimum sample size required to construct a 90% confidence interval for the population mean. Assume the population standard deviation is 0.20 inch.

(b) Repeat part(a) using a population standard deviation of 0.30 inch.

(c) Which standard deviation requires a larger samplesize? Explain.

(a) The minimum sample size with a population standard deviation of 0.20 inch is ____ balls.

(Round up to the nearestinteger.)

(b) The minimum sample size with a population standard deviation of 0.30 inch is _____ balls.

(Round up to the nearestinteger.)

(c) A population standard deviation of ____

inch requires a larger sample size because greater variability in the population requires a _______sample size to ensure the desired accuracy.