Table of contents
- 1. Intro to Stats and Collecting Data24m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically53m
- 4. Probability1h 29m
- 5. Binomial Distribution & Discrete Random Variables1h 16m
- 6. Normal Distribution and Continuous Random Variables58m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 5m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
4. Probability
Multiplication Rule: Independent Events
Problem 4.RE.7
Textbook Question
In Exercises 1–10, use the data in the accompanying table and express all results in decimal form. (The data are from “The Left-Handed: Their Sinister History,” by Elaine Fowler Costas, Education Resources Information Center, Paper 399519.)

Both Lefties If two of the study subjects are randomly selected with replacement, find the probability that they both write with their left hand.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Probability
Probability is a measure of the likelihood that an event will occur, expressed as a number between 0 and 1. In this context, it refers to the chance of randomly selecting two individuals who both write with their left hand. The probability can be calculated using the formula P(A) = number of favorable outcomes / total number of outcomes.
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Independent Events
Independent events are those whose outcomes do not affect each other. In this question, selecting one individual with replacement means that the first selection does not influence the second. Thus, the probability of both individuals being left-handed can be found by multiplying the probability of selecting a left-handed person in each trial.
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Replacement in Sampling
Sampling with replacement means that after an individual is selected, they are returned to the population before the next selection. This ensures that the total number of individuals remains constant for each selection, allowing for consistent probability calculations. In this case, it affects how the probabilities are computed for the two selections.
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