An occupational health inspector was interested in determining whether there is a difference in the loss in man-hours due to accidents by introducing a new safety programme. The inspector randomly sampled 10 different plants and recorded the loss in man-hours due to accidents before and after the safety programme was implemented. The data are displayed below:
(a) By hand, draw the appropriate dot plot(s) for this data set. (You should consider the design of this study to ensure the relevant plot(s) is drawn.) Comment on any features in the plot(s).
(b) (i) Is there an underlying mean difference in the loss in man-hours due to accidents before the safety programme was implemented and after the safety programme was implemented? Use SPSS to investigate this question. Interpret your results.
(ii) Is there an underlying median difference in the loss in man-hours due to accidents before the safety programme was implemented and after the safety programme was implemented? Use SPSS to investigate this question. Interpret your results.
(c) Which of the two tests from (b) is more appropriate for these data? Justify your answer.