I do not understand how to do these following questions:

1) For a sample of size n = 15,

the critical z-score for 82% confidence is (two-decimal accuracy, positive value only).

the critical t-score for 95% confidence is (three-decimal accuracy, positive value only).

2) An education support group wants to estimate the mean class size for elementary schools in the southeast. They want to have 99% confidence with error of no more than 2 students. A preliminary study gave a standard deviation of 8.4. How many classrooms should they sample?

3) Linda Silbers is a social scientist studying voter opinion about a city bond proposal for a light-rail mass transit system in Denver. Linda wants to estimate the proportion of voters who favor the bond. She wants to be 95% sure that her sample estimate of the proportion of voters who favor the bond is in error by no more than 5%. How large a sample should she use?


If a preliminary study showed that is approximately 73%, she should use a sample of voters.


If she has no preliminary estimate for p, she should use a sample of voters.

The mean value of land and buildings per acre from a sample of farms is $2400, with a standard deviation of $450. Between what two values do about 95% of the data lie? ( assume the data set has a bell- shaped deviation)