Assignment C

The data on technology firms from BusinessWeek measure company performance for the year 2009.

A. Observe the sample and describe the population the sample was likely taken from.

B. Divide the sample into firms involved in hardware* and those that are not. Calculate and compare the mean operating income level for the two groups. Can we say for sure that the population mean operating income for hardware firms is different from non-hardware firms? Explain.

C. Calculate and interpret the standard deviation in operating income for hardware and non-hardware firms. Calculate and interpret the coefficient of variation for the two groups. Which type of firm exhibits greater variation in operating income? Does the comparison of standard deviations tell the same story as the comparison of the coefficients of variation? Explain.

D. Generate the distribution in operating income for the full sample of firms. Use twelve classes in the distribution. Set the size of each class at $1,900 million. Make the endpoint of the first class equal to $1,868 million. Graph the distribution and discuss its skewness.

E. Test the assumption that the average firm within the population had a mean operating income of 1.95 billion dollars. Construct a 90% confidence interval for the population mean operating income and discuss whether your statistics agree or disagree with the assumption.

* Hardware includes the sectors: Communications; Computers, peripherals; Distributors; Electronic equipment; Semiconductors, equipment.