AP STATS
Show all your work. Indicate clearly the methods you use, because you will be graded on the correctness of your methods as well as on the accuracy of your results and explanation.
 
When reading the computer output, the regression equation is typically buried among other statistics. The value of the slope is the coefficient (Coef) of the explanatory variable. The value of the intercept is the coefficient (Coef) of the constant. For this problem, the regression equation is:
 
Number of aircraft = 2939.93 + 233.517 * (years since 1990)
 
This should help you with the rest of the work.
Lydia and Bob were searching the Internet to find information on air travel in the United States. They found data on the number of commercial aircraft flying in the United States during the years 1990-1998. The dates were recorded as years since 1990 was recorded as 0. They fit a least squares regression line to the data. The graph of the residuals and part of the computer output for their regression are given below.
 The graph has years since 1990 on the X-axis, and residuals on the Y-axis: the graph shows the following points: (0,18),(1,-20),(2.5,40),(3,-50),(4,25),(5,-40),(6,2),(7.5,40),(8,-20) Predictor Coef Stdev t-ratio P Constant 2939.93 20.55 143.09 0.000 Years 233.517 4.316 54.11 0.000
 
s= 33.43
 
a) Is a line an appropriate model to use for these data? What information tells you this?
b) What is the value of the slope of the least squares regression line? Interpret the slope in the context of this situation.
c) What is the value of the intercept of the least squares regression line? Interpret the intercept in the context of this situation.
d) What is the predicted number of commercial aircraft flying in 1992?
e) What was the actual number of commercial aircraft flying in 1992?