Chapter 14.3, Problem 29PB

Regression for telephone holding times Refer to the previous exercise. Let x₁ = 1 for the advertisement and 0 otherwise, x₂ = 1 for Muzak and 0 otherwise, and x₁ = x₂ = 0 for classical music. Likewise, let x₃ = 1 for repeating in 10-minute cycles and x₃ = 0 for repeating in 5-minute cycles. The display shows results of a regression of the telephone holding times on these indicator variables.

Regression for telephone holding times

1. a. Give the corresponding regression model for the population mean and show the equation for the population mean at each setting of the two factor levels. (Create a table similar to Table 14.11.)
2. b. State the prediction equation. Interpret the parameter estimates.
3. c. Find the estimated means for the six groups in the two-way cross-classification of type of recording and repeat time.
4. d. Find the estimated difference between the mean holding times for 10-minute repeats and 5-minute repeats, for a fixed recording type. How can you get this estimate from a coefficient of an indicator variable in the prediction equation?
5. e. Find a 95% confidence interval for the difference between the mean holding times for 10-minute repeats and 5-minute repeats.