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need some detailed steps for this Crash Day 193 49 23 21 55 28 57 Before After 1. The numbers in the Figure above indicate

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Crash Day 193 49 23 21 55 28 57 Before After 1. The numbers in the Figure above indicate the weather (overcast or not) of 434 location- matched triplets of days, one day on which a traffic accident took place, and two control days without an accident (the day before the accident and the day after the accident). This dataset could be analyzed as a 1:2-matched case-control. The Venn diagram presentation of the data is rather unconventional. In matched case-control studies the data could alternatively be presented in 2 x 2-tables exposed unexposed case bi control Ci di for each matched set i = 1,. ... 434. We denote n = a; t b; t c t di. (a) [5 Marks] We note that there are six types of location-specific 2 x 2-tables with the same exposure-case configuration. List these tables (i.e. different combinations of the numbers ai, bi, c; and di) and their counts.(b) [3 Marks] The null hypothesis assumes that there is no relationship between being a case and being exposed. Under the null hypothesis the distribution of the cell count a; conditional on the row and column marginals is hypergeometric. Find E(q; | 4; + q) and Var(a; [ a; + c) under the null. (c) [3 Marks] Test the null hypothesis of no association between weather and accidents using the Cochrane-Mantel-Haenszel (CMH) test statistic, given by CMla -[M Elaila + c)) Ell Var(a; | a; + Gi) which is asymptotically distributed as x' with one degree of freedom. Note: Xo.9s (1) = 3.84. (d) [4 Marks] Let's assume we have the following table is a triplet specific contingency table from a 1:2 matched case control study. exposed unexposed Total case control C d Total atc b+d The odds of being exposed in the case groups is o times of the odds of being exposed in the control group. Also, let's assume that P(@ = 1) = 14 00 and P(c = 1) = 1+ 0 Show that, P(a =1 [ a + c=1)= 2+0 (Hint: The 2 in the denominator comes from 2 controls)

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