Confidence Intervals, Proportions, Mean, Standard Deviation and Variance

1. Three hundred of 450 drivers surveyed indicated that they would consider bying retread tires. Find a 95% confidence interval for the true proportion of all who might buy retread tires.

2. Insurance industry analysts report that the average amount of life insurance in effect in Virginia is $92,500 with a sample standard deviation of $8,400. A newspaper conducted a random survey of 64 Virginia families. What is the probability that the average amount of insurance in effect for these families is more than $95,000?

3. A national health foods manufacturer wishes to determine the average amount people are willing to spend annually on health foods. If previous data indicate that o=variance=7.50, how large should the sample be to ensure with 95% confidence that estimate is within $1.00 of the true value?

4. A traffic survey revealed that the speeds of vehicles along a dangerous stretch of interstate follow a normal distribution with mean 50 mph and standard deviation 8 mph. What speed limit should be posted so that only 8% of all drivers monitored are guilty of speeding?

5. Bank officials claim that the average amount of money in savings accounts at all branches of the Commerce Bank is $7,500, with a standard deviation of $650. Many random samples of size 100 are taken.
a. the mean of these samples

Confidence Intervals, Proportions, Mean, Standard Deviation and Variance are investigated. The solution is detailed and well presented. The response received a rating of "5/5" from the student who originally posted the question.

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