1.

A random sample of 93 observations produced a mean x=25.5 and a standard deviation sequals=2.4.

a. Find a95% confidence interval for .

b. Find a90% confidence interval for .

c. Find a99% confidence interval for .

2.

The mean and standard deviation of a random sample of n measurements are equal to 34.4 and 3.6, respectively.

a. Find a 90% confidence interval for if n=121.

b. Find a 90% confidence interval for if n=484.

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 coefficientfixed?

3.

If you wish to estimate a population mean with a margin of error ME=0.23 using a95% confidence interval and you know from prior sampling that 2 is approximately equal to 7.3, how many observations would have to be included in yoursample?

The number of observations that would have to be included in your sample is