# Finding 98% and 99% Confidence Intervals

1. What is the 99% confidence interval for the variance of exam scores for 25 algebra students, if the standard deviation of their last exam was 10.7?

2. In a sample of 60 mice, a biologist found that 42% were able to run a maze in 30 seconds or less. find the 98% limit for the population proportion of mice who can run that maze in 30 seconds or less.

3. What is the 99% confidence interval for the standard deviation of birth weights at County General Hospital, if the standard deviation of the last 28 babies born there was 1.3 pounds?

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#### Solution Preview

1. At 99% level, the critical value is 9.886 and 45.559 from chi square table.

So lower limit=(25-1)*10.72/45.559=60.31 and ...

#### Solution Summary

The solution gives detailed steps on finding 98% and 99% confidence intervals for the population variance and population proportion respectively.