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Sampling/Confidence Intervals

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I would like to have the following sample questions answered in EXCEL format, so that I can see the formulas used.

Thanks in advance!

1. The mean score of a college entrance exam is 500; the standard deviation is 75. The score are normally distributed. What percent of the students scored below 320?

2. On a very hot summer day, 5 percent of the production employees at Midland State Steel are absent from work. The production employees are to be selected at random for a special in-depth study on absenteeism. What is the probability of selecting 10 production employees at random on a hot summer day and finding the none of them are absent?

3. For the normal distribution, the mean plus and minus 1.96 standard deviations will include about what percent of the observations?

4. Sweetwater and Associates write weekend trip insurance at a very nominal charge. Records show that the probability that a motorist will have an accident during the weekend and file a claim is 0.05.

Suppose they wrote 20 policies for the coming weekend, what is probability that exactly two claims will be filed?

5. Chances are 50-50 that a newborn baby will be a girl. For families with 5 children, what is the probability that all the children are girls?

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Solution Summary

The solution gives detailed on solving 5 questions using either normal distribution or binomial distribution using Excel.

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See Also This Related BrainMass Solution

Normal Distribution, Sampling distribution, Confidence interval

1) The distribution of sample mean for samples of 500 homes is normal with a mean of 2.64 and a standard deviation of 0.06. Suppose you select a random sample of n=500 homes and determine that the mean number of people per home for this sample id 2.55. How many standard deviations is the sample mean of the sampling distribution? What is the probability that a second sample would be selected with a mean less than 2.55?

2) You have 42% of a company are woman, you also know the normal mean is at .42 and a standard deviation of 0.21. Suppose you take a random sample of employees and find that the proportion of women is 0.45. How many standard deviations is the sample mean of the sampling distribution? What is the probability that a second sample would be selected with a proportion greater than 0.45?

3) Telephones: A random sample of n=31 homes is asked the number of telephones in a home: data as follows;

1 0 2 3 2 3 4 2 1 1 2
4 3 2 3 3 0 1 0 1 3 2
4 3 2 1 4 0 1 2 3

a) What's the mean # of telephones for the sample?
b) What is the standard deviation?
c) Whats the 95% confidence interval for the estimate?
d) Whats the best estimate for the mean number of telephones of all homes?

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