Math Problem Statement

Assume that 9​% of people are​ left-handed. If 6 people are selected at​ random, find the probability of each outcome described below. Find the probability that there are some lefties among the 6 people.

Solution

We are given that 9% of people are left-handed, which means the probability of selecting a left-handed person is p=0.09p = 0.09. The probability of selecting a right-handed person is 1p=0.911 - p = 0.91. We are asked to find the probability that there are some left-handed people among 6 randomly selected individuals.

This is a binomial probability problem where:

  • The number of trials n=6n = 6,
  • The probability of success (selecting a left-handed person) p=0.09p = 0.09,
  • The probability of failure (not selecting a left-handed person) 1p=0.911 - p = 0.91.

Step 1: Complementary Probability Approach

The easiest way to find the probability that there are some left-handed people is to use the complement rule. First, we calculate the probability that none of the 6 people are left-handed, then subtract this value from 1 to find the probability that at least one person is left-handed.

The probability that none of the 6 people are left-handed is: P(none left-handed)=(0.91)6P(\text{none left-handed}) = (0.91)^6

Now, calculate this: P(none left-handed)=0.9160.606P(\text{none left-handed}) = 0.91^6 \approx 0.606

Step 2: Find the Probability of "Some Left-Handed"

The probability of having some left-handed people is the complement of the probability that none are left-handed: P(some left-handed)=1P(none left-handed)P(\text{some left-handed}) = 1 - P(\text{none left-handed}) P(some left-handed)=10.606=0.394P(\text{some left-handed}) = 1 - 0.606 = 0.394

Thus, the probability that there are some left-handed people among the 6 selected is approximately 0.394, or 39.4%.

Would you like more details or further questions?

Here are 5 related questions to explore:

  1. What is the probability that exactly 2 of the 6 people are left-handed?
  2. What is the probability that all 6 people are right-handed?
  3. How does the binomial distribution change if the probability of being left-handed increases to 20%?
  4. How many left-handed people would you expect to find among 10 randomly selected people?
  5. What is the probability that fewer than 3 people are left-handed among 8 selected individuals?

Tip: The complement rule is often helpful when finding the probability of "at least one" event happening!

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Math Problem Analysis

Mathematical Concepts

Probability
Binomial Distribution
Complement Rule

Formulas

P(none left-handed) = (0.91)^6
P(some left-handed) = 1 - P(none left-handed)

Theorems

Binomial Probability Theorem
Complement Rule

Suitable Grade Level

Grades 9-12