9.1

25.

  1. type answer here.

p=417/2306=0.18

  1. type answer here.

Since 23060.180.82=340.37 >10 and the sample size is no more than 5% of the population, the requirements for constructing a confidence interval about p are satisfied.

  1. type answer here.

E=1.645√（0.180.82/2306）=0.0132 0.18-0.0132=0.1668 0.18+0.0132=0.1932 the confidence interval is 0.1668-0.1932

  1. type answer here.

We are 90% confident that the proportion of adult Americans aged 18 and older who have donated blood in the past two years is between 0.1668 and 0.1932

26.

  1. type answer here.

p=496/1153=0.430

  1. type answer here.

Since 11530.4300.570=282.60>10 and the sample size is no more than 5% of the population, the requirements for constructing a confidence interval about p are satisfied.

  1. type answer here.

E=1.96√(0.4300.670/1153)=0.029 0.430-0.029=0.401 0.430+0.029=0.459 The confidence interval is 0.401-0.459

  1. type answer here.

We are 95% confident that the proportion of workers and retirees in the United States 25 years of age and older who have less than $10,000 in savings is between 0.401 and 0.459

27.

  1. type answer here.

p=521/1003=0.519

  1. type answer here.

Since 0.5190.4811003>10 and the sample size is no more than 5% of the population, the requirements for constructing a confidence interval about p are satisfied.

  1. type answer here.

E=1.96√(0.5190.481/1003)=0.031 The confidence interval is 0.488-0.55, meaning that we are 95% confident that the proportion of adult Americans think televisions are a luxury they could do without is between 0.488 and 0.55

  1. type answer here.

It is possible that a supermajority of adult Americans believe that television is a luxury they could do without, but it is not likely, because the upper bound is 0.55 which is less than 0.6 and we are 95% confident that the proportion is between 0.488 and 0.55

  1. type answer here.

p=(1003-521)/1003=0.481 E=1.69√(0.5190.481/1003)=0.031 0.481-0.031=0.45 0.481+0.031=0.512 The confidence interval is 0.45-0.512

28.

  1. type answer here.

P=768/1024=0.75

  1. type answer here.

Since 10240.750.25>10 and the sample size is no more than 5% of the population, the requirements for constructing a confidence interval about p are satisfied.

  1. type answer here.

E=2.575√(0.750.25/1024)=0.035 The confidence interval is 0.715-0.785

  1. type answer here.

It is possible that the proportion of adult Americans aged 18 or older for which the issue of family values is extremely or very important in determining their vote for president is below 70%, but is not likely, because we are 99% confident that the proportion is between 0.715-0.785

  1. type answer here.

p=1-0.75=0.25 E=2.575√(0.750.25/1024)=0.035 The confidence interval =0.215-0.285

29.

  1. type answer here.

p=26/234=0.111 E=1.96√(0.1110.889/234)=0.040 The confidence interval is 0.071-1.151

  1. type answer here. E=2.575√(0.1110.889/234)=0.053 The confidence interval is 0.058-0.164

  2. type answer here.

As the level of confidence increases, the margin of error increases.