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Probability of selecting a person from a group or committee: Overview
Problems about picking people from groups or committees are extremely common types of questions in probability and statistics. This article shows you the odds of picking a certain person FROM a committee. If you want to figure out possibilities for choosing people FOR committees, you’ll want to check out our articles on figuring out combinations, like this one: 5 Choose 3.
Probability of selecting a person from a group or committee: Steps
Sample problem: At a school board meeting there are 9 parents and 5 teachers. Two teachers and 5 parents are female. If a person at the school board meeting is selected at random, find the probability that the person is a parent or a female.
Step 1: Make a chart of the information. In the sample question, we’re told that we have 5 female parents, 2 female teachers, 9 total parents and 5 total teachers.
Step 2: Fill in the blank column(s). For example, we know that if we have 9 total parents and 5 are female, then 4 must be male.
Step 3: Add a second total to your chart to add up the columns.
Step 4: Add up the probabilities. In our case we were asked to find out the probability of the person being a female or a parent. We can see from our chart that the probability of being a parent is 9/14 and the probability of being a female is 7/14.
9/14 + 7/14 = 16/14
Step 5:Subtract the probability of finding both at the same time. In our case, we subtract female parents.
16/14 – 5/14 = 11/14
You’re done with the Probability of selecting a person from a group or committee!
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