1 of 4

  • An article in the Journal of the Environmental Engineering Division [“Least Squares Estimates of BOD Parameters” (1980, Vol. 106, pp. 1197–1202)] took a sample from the Holston River below Kingport, Tennessee, during August 1977. The biochemical oxygen demand (BOD) test is conducted over a period of time in days. The resulting data follow:
  • Time (days) (x): 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20.
  • BOD (mg/liter) (y): 0.6, 0.7, 1.5, 1.9, 2.1, 2.6, 2.9, 3.7, 3.5, 3.7 3.8.

2 of 4

  • (a) Assuming that a simple linear regression model is appropriate, fit the regression model relating BOD (y) to the time (x)?
  • (b) What is the estimate of expected BOD level when the time is 15 days?
  • (c) Suppose that the time used is six days. Calculate the fitted value of y and the corresponding residual.

3 of 4

  • A randomly selected high temperatures at various cities on a single day and the elevation of the city is given in the below table:

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  • A) Find a regression equation for elevation (x) and high temperature (y) on a given day.
  • B) Use the regression equation to estimate the high temperature on that day at an elevation of 5500 ft.

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4 of 4

  • C) Find the correlation coefficient
  • D) Is there enough evidence to show a negative correlation between elevation and high temperature? Test at the 5% level.
  • E) Is there enough evidence to show that there is significance of regression between x and y? Test at the 5% level.

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