Refer to Exercise.Consider the following pairs of measurements, saved in the LM9_95 file.x...

Refer to Exercise.

Consider the following pairs of measurements, saved in the LM9_95 file.

For these data, SSxx = 38.900, SSyy = 33.600, SSxy = 32.8, and

a. Construct a scatterplot of the data.

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b. Plot the least squares line on your scatterplot.

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c. Use a 95% confidence interval to estimate the mean value of y when xp = 6. Plot the upper and lower bounds of the interval on your scatterplot.

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d. Repeat part c for xp = 3.2 and xp = 0.

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e. Compare the widths of the three confidence intervals you constructed in parts c and d , and explain why they differ.

a. Using no information about x , estimate and calculate a 95% confidence interval for the mean value of y.[ Hint: Use the one-sample t methodology of Section 7.3.]

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b. Plot the estimated mean value and the confidence interval as horizontal lines on your scatterplot.

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c. Compare the confidence intervals you calculated in parts c and d of Above Taken Exercise  with the one you calculated in part a of this exercise. Does x appear to contribute information about the mean value of y ?

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d. Check the answer you gave in part c with a statistical test of the null hypothesis H0: β1 = 0 against Ha: β1 ≠ 0. Use α =.05.