Can keeping cows out of a creek on ranchland improve the water quality? To answer this question environmental researchers measured the coliform on grazed ranch land. Then, a fence was installed along one of the creeks to keep the cattle out. Several weeks later, coliform counts were measured again along the two creeks at the same locations (i.e., the locations formed pairs).The accompanying table summarizes the coliform data (MPN/100ml).28

(a) Use an appropriate t test to test to assess the statistical significance of the reduction in coliform along the fenced creek after the installation of fencing. Use a non directional alternative and a = 0.10.
(b) Briefly explain why considering the data for fenced creek data alone, one cannot determine if the fencing was effective.
(c) Use an appropriate t test to test to compare the reduction in coliform along the fenced and control creeks. Use a non directional alternative and a = 0.10. (You may use df ‰ˆ 12).
(d) Is the answer to part (c) consistent with the hypothesis that the fencing is effective?

Transcribed Image Text:

Fenced creek Control creek Coliform (n 8 locations) (n 7locations) (MPN/100m) Men SD Mean SD Before fencing 256.1 57.8 284.3 91.4 After fencing 225.0 75.2 269.0 8L.5 31 17.8 15.3 16.3 Difference