A medical sociologist internist is curious as to whether there is any connection

Question

A medical sociologist internist is curious as to whether there is any connection between various behaviors that could be viewed as risk taking. She collects data from her records on 162 patients concerning their usage of seat belts and of cigarettes. For the following cross-tabulation, calculate Chi- Square. Smoker Non-Smoker Always use seat belts 10 Usually use seat belts 30 Seldom use seat belts 46 32 26 18 D Question 5 0.2 pts Using the data from Question 4, what is the critical value of Chi-Square?

Explanation / Answer

Question 4 . The contigency table

Here Expected values

(i) for always and smoker = 86 * 42 /162 = 22.30

(ii) for always and non smoker = 76 * 42/ 162 = 19.70

(iii) for usually and smoker = 86 * 56/162 = 29.73

(iv) for usually and non- smoker = 76 * 56/ 162 = 26.27

(v) for Seldom and smoker = 86 * 64/ 162 = 33.98

(vi) for seldom and non- smoker = 76 * 64/162 = 30.02

The expected table

Here now we will calculate value of chi - square

X2 = (Oi - Ei)2 /Ei

calculating value of chi - square for each cell of contigency table.

Chi - square X2 = 23.532

Question 5

here dF = (2-1) * (3-1) = 2 and alpha = 0.0.5

X2 (critical) = 5.992

Question 6

here X2 > X2 (critical) so we reject the null hypothesiss and can say that seat belt and smoking are related to each other.

Smoking Habits Smoker Non- Smoker Total Seat Belts Always 10 32 42 Usuallly 30 26 56 Seldom 46 18 64 Total 86 76 162

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