So I'm doing some basic probability problems for homework, and we just recently went over the Inclusion-Exclusion prinicple, which I'm assuming this problem deals with, which is as follows.
Shoppers can pay for their purchases with cash, a credit card, or a
debit card. Suppose that the proprietor of a shop determines that 63%
of her customers use a credit card, 23% pay with cash, and the rest
use a debit card. What is the probability that a person will not use a credit card? What is the probability that a person pays in cash or with a credit card?
Now, it's my understanding that these percentages they give us don't overlap (i.e. a person won't pay part of their bill with cash, and the rest on a card, etc. etc.) So it seems relatively straightforward in the sense that only 14% of people pay with a debit card. So for the first part of the problem, wouldn't the answer simply be to add 14% and 23%? And the second would simply be the addition of 63% and 23%?
I have a feeling I'm misunderstanding something, as I'm not getting the problem right.
Best Answer
Reading the problem and your explanation, I think that you are completely right. If 63% of the people pay with credit, then 100%-63% = 14+23% don't. Then for the other question, 63%+23% would equal the amount of people who pay with credit or cash. So yeah, your reasoning is right.