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(Use Excel for all your work)

1. The observations in the Excel data file SHEET 1 are the ages of a random sample of 8 men in a bar. It is known that the ages are normally distributed with a standard deviation of 10. Determine the 95% confidence interval estimate of the mean.

2. It is known that the amount of time needed to change the oil in a car is normally distributed with a standard deviation of 5 minutes. The amount of time to complete a random sample of 10 oil changes was recorded and listed in the Excel data file SHEET 2. Compute the 99% confidence interval estimate of the mean of the population.

Notes:

Questions 1-2:

Step 1: Use AVERAGE function to find the sample mean from the data.

Step 2: Use the function CONFIDENCE.NORM (Formulas -> More functions -> Statistical) to combine the mean and the population standard deviation (given in the problem) along with the given value of α using the formulation:

Sample mean ± CONFIDENCE.NORM(alpha, std. dev., sample size)

Question 3:

Use normdist function: normdist(x,mean, std.dev, cumulative), where cumulative = TRUE if computing P(X < k) and cumulative = FALSE if computing P(X = k). See the practice problems from Chapter 8 for more info, if desired.

Misc:

Clearly state the functions you are using along with the input arguments (if clicking on the answer displays the function at the top, that’s ok too).

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