Fugitive dust plumes generated by farm equipment can be hazardous to human health. In the Journal of Agricultural, Biological, and Environmental Sciences (Mar. 2001). environmental engineers developed a model for dust particle concentrations in plumes produced by a tractor operating in a wheat field. The tractor traveled along six parallel, equi-length paths in the field. A remote sensing instrument with a laser beam, placed at the edge of the field, measured the particulate matter in the dust every .5 seconds. Unfortunately, a few of the measurements were censored (i.e., higher than the signal level of the instrument). This usually occurred when the tractor was a short distance from the instrument's laser beam. The table on the next page shows the number of censored measurements for each of the six tractor lines.
a. Calculate and compare the sample proportion of censored measurements for the six tractor lines.
b. Do the data provide sufficient evidence to indicate that the proportion of censored measurements differs for the six tractor lines? Test using α = .01.
c. Comment on the practical versus statistical significance of the test.

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Tractor Line Uncensored Measurements Measurements Censored Totals 6,047 4.456 6,821 5,889 9,873 4.607 175 236 319 231 480 187 6.222 4,692 7140 6,120 10,353 4.794 70 Totals 37693 1,628 39,321