42. The probability of a type II error for the t test for H0:

b1  b10 can be computed in the same manner as it was computed for the t tests of Chapter 9. If the alternative value of b1 is denoted by , the value of is rst calculated, then the appropriate set of curves in Appendix Table A.17 is entered on the horizontal axis at the value of

d, and b is read from the curve for n  2 df. An article in the J. Public Health Engrg. reports the results of a regression analysis based on n  15 observations in which x  lter application temperature (C) and y  % ef ciency of BOD removal. Here BOD stands for biochemical oxygen demand, and it is a measure of organic matter in sewage. Calculated quantities include xi 

402,  11,098, s  3.725, and  1.7035.

Consider testing at level .01 H0: b11, which states that the expected increase in % BOD removal is 1 when lter application temperature increases by 1C, against the alternative Ha: b1 1. Determine P(type II error) when b1  2, s  4.