Question

1. A survey of 25 randomly selected customers had the mean 33.04 years and the standard deviation 10.45 years.

1. What is the standard error of the mean?

2. How would the standard error change if the sample size had been

            400 instead of 25? (Assume that the sample standard deviation didn't change.)

2. Find the degrees of freedom for n=60.

3. Find the t critical value for n=60 for 90% CI for mean.

4. A survey of 25 randomly selected customers had the mean 32.88 years and the standard deviation 10.03 years.

1. Construct a 95 % confidence interval for the mean age of all customers, assuming that the assumptions and conditions for the confidence interval have been met.
2. How large is the margin of error?

3. (c) How would the confidence interval change if you had assumed that the standard deviation was known to be 11.0 years?

5. A survey of 25 randomly selected customers has the mean is 32.52 years and the standard deviation is 8.14 years.8.14 years.

1. ​What is the standard error of the​ mean?

2. How would the standard error change if the sample size had been 225 instead of 25​?

​            (Assume that the sample standard deviation​ didn't change.)

6. A survey of 25 randomly selected customers found the ages shown​ (in years). The mean is 32.84 years and the standard deviation is 9.58 years.

1. ​Construct a 99​% confidence interval for the mean age of all​ customers, assuming that the assumptions and conditions for the confidence interval have been met.

2. ​How large is the margin of​ error?

      (​c) How would the confidence interval change if you had assumed that the standard

             deviation was known to be 10.0 ​years?

Answer 1

1