Two hundred people were asked if they had read a book in the last month. The accompanying contingency table, cross-classified by age, is produced. The probability that a respondent is at least 30 years old is the closest to ________.
A) 0.33
B) 0.46
C) 0.50
D) 0.65

Question

Two hundred people were asked if they had read a book in the last month. The accompanying contingency table, cross-classified by age, is produced.  The probability that a respondent is at least 30 years old is the closest to ________.
A) 0.33 
B) 0.46 
C) 0.50 
D) 0.65

Quizplus · Accepted Answer

The total number of respondents in the table is 200. The sum of the frequencies in the first two columns (corresponding to those under 30 and those at least 30) is 90 + 110 = 200, which covers all respondents. Therefore, the probability of a respondent being at least 30 years old is 110/200 = 0.55. The closest option to this is C) 0.50.

Two Hundred People Were Asked If They Had Read a Book