Week Two Book Work

5.4 A random sample of 90 observations produced a mean 25.9 and a standard deviation s=2.7
a. Find an approximate 95% confidence interval for the population mean m
b. Find an approximate 90% confidence interval for m
c. Find an approximate 99% confidence interval for m
5.8 The mean and standard deviation of a random sample of n measurements are equal to 33.9 and 3.3, respectively.
a. Find a 95% confidence interval for m if n= 100
b. Find a 95% confidence interval for m if n =400
c. Find the widths of the confidence intervals found in parts a and b.What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?
5.25 The following random sample was selected from a normal distribution: 4, 6, 3, 5, 9, 3.
a. Construct a 90% confidence interval for the population mean m 5 +- 1.88
b. Construct a 95% confidence interval for the population mean m 5+- 2.39
c. Construct a 99% confidence interval for the population mean m 5+- 3.75
d. Assume that the sample mean and sample standard deviation s remain exactly the same as those you just calculated but are based on a sample of n=25 observations rather than n=6 observations. Repeat parts a–c. What is the effect of increasing the sample size on the width of the confidence intervals? a)5+- 78.5+-94.5+-1.28
b) the sample size of the width will decrease

5.37 For the binomial sample information summarized in each part, indicate whether the sample size is large enough to use the methods of this chapter to construct a confidence interval for p. a n= 400 p =.10 Yes b.n= 50 p = .10 NO
c. n=20 Yes and No d.n=20 p = .3 NO

5.41 Is Starbucks coffee overpriced?The Minneapolis Star Tribune
(August 12, 2008) reported that 73% of Americans say that
Starbucks coffee is overpriced.The source of this information was a national telephone survey of 1,000 American adults conducted by Rasmussen Reports.
a. Identify the population