The following data give information on the ages (in years) and the numbers of breakdowns during the last month for a sample of seven machines at a large company.

a. Taking age as an independent variable and number of breakdowns as a dependent variable, what is your hypothesis about the sign of B in the regression line? (In other words, do you expect B to be positive or negative?)
b. Find the least squares regression line. Is the sign of b the same as you hypothesized for B in part a?
c. Give a brief interpretation of the values of a and b calculated in part b.
d. Compute r and r2 and explain what they mean.
e. Compute the standard deviation of errors.
f. Construct a 99% confidence interval for B.
g. Test at a 2.5% significance level whether B is positive.
h. At a 2.5% significance level, can you conclude that p is positive? Is your conclusion the same as in part g?

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Age (years) Number of breakdowns 10 5 4 12 72 12 7 28 13 9