23. Oakland passengers The scatterplot below shows the number of passengers departing from Oakland (CA) airport month by month since the start of 1997. Time is shown as years since 1990, with fractional years used to represent each month. (Thus, July of 1997 is 7.5—halfway through the 7th year after 1990.) (www.oaklandairport.com)

Here’s a regression and the residuals plot:
Dependent variable is Passengers R@squared = 71.1% s = 104330 Variable Coefficient Constant 282584 Year - 1990 59704.

a) Interpret the slope and intercept of the model.

b) What does the value of R2 say about the model?

c) Interpret se in this context.

d) Would you use this model to predict the numbers of passengers in 2010 (Years Since 1990 = 20)? Explain.

e) There’s a point near the middle of this time span with a large negative residual. Can you explain this outlier?

1,200,000- 1,000,000- Passengers 800,000 7.5 10.0 12.5 15.0 Years Since 1990