# Confidence Limits

(a) Using Excel, find   the mean, median, and mode for each quiz. Then also find the Range and   Standard deviation(see supplemental notes for week 3).

Test 1  Test 2  Test 3  Test 4        60   65   66   10         60   65   67   49         60   65   70   70         60   65   71   80         71   70   72   85         73   74   72   88         74   79   74   90         75   79   74   93         88   79   95   97         99   79   99   98

(b) Do these   measures of central tendency agree? Explain. What could the measures of dispersion tell us about the results of the   quiz? We use descriptive statistics   computations to allow us to describe data

Exercise 4-2

Confidence Interval

An experiment involves selecting a random sample of 256 middle managers. We would like to know the   mean salary (annual income). The sample mean salary is 45,000, and the sample standard deviation is \$2,000.

Calculate the 95% confidence interval, showing the confidence limits. Hint, because the sample size is greater than 30, we use the Z factor for 95%.

INCLUDE AN EXCEL SPREADSHEET SHOWING YOUR   WORK TO CALCULATE THE 95% CONFIDENCE INTERVAL.

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