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# Probability and confidence interval problems

A. Margaret Morris just correctly computed a standard deviation of 6.0 from a sample of 50 observations. What is the variance of Margaret's sample?

b. Kim Fernando has just found the variance of a sample of 32 observations to be 64.0 by using a formula that is programmed into her new calculator. Therefore, what is the sample standard deviation?

c. A store manager found that 20 of his 50 ties in stock are striped. What is the probability that a random selection of a tie to show a customer will be striped?

d. If the probability that Jeff Springs will win the high jump at the state meet is 0.2, the probability that someone other than Jeff wins the high jump is?

e. A university wants to estimate the average amount of money that students spend on textbooks in a semester. It takes a random sample of 45 students and finds that an average amount of money spent was \$282 with a standard deviation of \$21. Find a 95% confidence interval estimate for the true mean amount of money spent on textbooks in a semester.

#### Solution Summary

The solution provides step by step method for the calculation of Probability and confidence interval problems . Formula for the calculation and Interpretations of the results are also included.

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