Given the contingency table shown here,what is the probability that a mother smoked during pregnancy or that she graduated from college?
A) .0111
B) .2591
C) .3861
D) .7850

Question

Given the contingency table shown here,what is the probability that a mother smoked during pregnancy or that she graduated from college? 
A) .0111 
B) .2591 
C) .3861 
D) .7850

Quizplus · Accepted Answer

To calculate the probability of a mother smoking during pregnancy or graduating from college, we need to sum the probabilities of those two events. We can see from the contingency table that there are 167 mothers who smoked during pregnancy, 327 mothers who graduated from college, and 90 mothers who both smoked during pregnancy and graduated from college. To get the total number of mothers who fall into either category, we need to add the number who only smoked during pregnancy (i.e. 167 - 90 = 77) to the number who only graduated from college (i.e. 327 - 90 = 237) and then add the number who fall into both categories (i.e. 90). Therefore, the total number of mothers who either smoked during pregnancy or graduated from college is 77 + 237 + 90 = 404. The probability of selecting one of these mothers at random is therefore 404/1044 = 0.3861 or approximately 0.39. So the best choice is C.

Given the Contingency Table Shown Here,what Is the Probability That