The prices of 23” TV sets sampled by a consumer guide were as follows: $400, $600, $550, $450, $700, $500, and $650. Build a 98 percent confidence interval for the mean.

Question 1

 

Design a 95 percent confidence interval for the proportion of defectives in a large lot, if a sample of 200 showed 12 defectives.

 

 

 

 

Question 2

 

The prices of 23” TV sets sampled by a consumer guide were as follows: $400, $600, $550, $450, $700, $500, and $650. Build a 98 percent confidence interval for the mean.

 

 

 

 

Question 3

 

You wish to estimate with 95 percent confidence the proportion of families that own two cars.

a)       How large a sample do you need if you allow an error of up to 2 percent in each direction?

 

b)       What will be the sample size if your prior estimate for p was 0.7?

 

 

 

Question 4

 

A sample of 400 people getting a tax refund showed the mean to be $900 and standard deviation to be $200.

a)       Design a 99 percent confidence interval.

 

b)       How large a sample do you need if you want the error to be no more than $10?