Jensen Tire & Auto is in the process of deciding whether to
purchase a maintenance contract for its new computer wheel
alignment and balancing machine. Managers feel that maintenance
expense should be related to usage, and they collected the
following information on weekly usage (hours) and annual
maintenance expense (in hundreds of dollars).
Annual Maintenance Expense: 17 22 30 37 47 31 33 39 52
Weekly Usage: 13 10 20 28 32 17 24 31
40
a) Construct a scatter diagram for these data. Does the scatter
diagram exhibit a linear relationship?
b) Find the least squared regression line.
c) Plot the regression line on the scatter diagram of part A and
show the errors by drawing vertical lines between scatter points
and the regression line.
d) In the sample, one machine had Annual Maintenance Expense of
37 with Weekly Usage of 28. What is the predicted Annual
Maintenance Expense?
e) Find the error for this observation in part d.
f) Calculate the standard deviation of errors.
g) Compute the coefficient of determination.
h) Construct a 99% confidence interval for B.
h) Test at the 5% significance level whether B is different from
zero.
Jensen Tire & Auto is in the process of deciding whether to purchase a maintenance contract for its new computer wheel a
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