Confidence Interval - Single Population Standard Deviation & Variance

1.You would like to construct a confidence interval for the standard deviation for the time it takes to prepared a tax return.You randomly select 18 tax returns and get a sample standard deviation of 8.6 minutes.Construct a 95% confidence interval for the standard deviation for the time it takes to prepared a tax return.

(Round margin of error to 4 decimal places at the end) and (express the final answer with 4 decimal places- such as 7.1234 to 15.2468).Make sure to use values from your tables.Test statistics, confidence interval values and probabilities generated by your calculator should not be used.

2.You would like to construct a confidence interval for the variance of the number of documents that are used in preparing a tax return.You randomly select 54 tax returns and get a sample variance of 3.4 documents.Construct a 90% confidence interval for the variance of the number of documents that are used in preparing a tax return.

(Round margin of error to 4 decimal places at the end) and (express the final answer with 4 decimal places- such as 7.1234 to 15.2468).Make sure to use values from your tables.Test statistics, confidence interval values and probabilities generated by your calculator should not be used.