4. Analyzing data: Smoking and accidents For several years a general 'non-smoking' day has been held annually on the second Wednesday in March. Data have been collected to study if 'non-smoking' has any influence on number of workrelated accidents. To try a control for many other factors that may also influence work accidents, data are compared to number of work accidents on the closest Wednesday before non-smoking day. Here are the data: Year Wednesday before Non-smoking Wednesday 1987 516 540 1988 610 620 1989 581 599 1990 586 639 1991 554 607 1992 632 603 1993 479 519 1994 583 560 1995 445 515 1996 522 556 a. Plot the data in a graph. Do you see any pattern? b. How many more - or less - accidents were there on average on Non-smoking day compared to a normal working day? c. Also calculate the relevant SD's. Explain in words what they express. d. Also calculate the 95 % CI's. How do the CI's relate to SD's? e. Test if there is a difference in work accidents - or not. Explain your results. f. A second question explored was if there is any trend in number of accidents on normal working days with time. Test if there is any trend in work accidents with time - or not. Explain your choice of test and your results.