Refer to Exercise 11.50.
(a) Construct a 95% confidence interval for the slope of the regression line.
(b) Obtain a 90% confidence interval for the expected y value corresponding to x = 4 days.
Exercise 11.50
Last week's total number of hours worked by a student, y, depends on the number of days, x, he reported to work last week. Suppose the data from nine students provided

(a) Plot the scatter diagram.
(b) Calculate ,, Sxx ,Syy and Sxy
(c) Determine the equation of the least squares fitted line and draw the line on the scatter diagram.
(d)Find the predicted number of hours y corresponding to x = 3 days.

y86 7 1015 12 13 19 18