Hi I tried adding proportion of adults (164/336) + proportion of no correct answers (61/336) but was marked wrong. Correct answer was 0.6339 I don't get why :
What is the probability that a randomly selected participant is an adult or had no correct answers?
# of Correct Answers Total
0 1 2 3 4
Adults : 12 30 43 39 40 164 (TOTAL)
Students: 49 14 10 52 47 172 (TOTAL)
The totals of 0 wrong were 12 + 49 = 61 and so on
Total Adults and students were 164 + 172 = 336
Can someone show the calculation ?
What is the probability that a randomly selected participant is an adult or had no correct answers?
# of Correct Answers Total
0 1 2 3 4
Adults : 12 30 43 39 40 164 (TOTAL)
Students: 49 14 10 52 47 172 (TOTAL)
The totals of 0 wrong were 12 + 49 = 61 and so on
Total Adults and students were 164 + 172 = 336
Can someone show the calculation ?
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you have double counted adults with no correct answers
the formula is P(A or B) = P(A) + P(B) - P(A & B)
= (164 + 61 - 12)/336
= 213/336 = 0.6339 <------ qed
the formula is P(A or B) = P(A) + P(B) - P(A & B)
= (164 + 61 - 12)/336
= 213/336 = 0.6339 <------ qed