13. Students A physics class has 40 students. Of these, 12 students are physics majors and 16 students are minoring in math. Of the physics majors, three are minoring in math. Find the probability that a randomly selected student is minoring in math or a physics major.
Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 53m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample2h 19m
- 10. Hypothesis Testing for Two Samples3h 22m
- 11. Correlation1h 6m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
4. Probability
Addition Rule
Problem 3.3.24c
Textbook Question
Mental Health A survey asks 4805 parents the severity of the mental issues they experienced from the coronavirus pandemic. The results are shown in the table. A parent is randomly selected from the sample. Find the probability of each event. (Adapted from Kaiser Family Foundation)

c. The parent did not have major mental health issues or is a mother.

1
Step 1: Understand the problem. We are tasked with finding the probability that a randomly selected parent either did not have major mental health issues or is a mother. This involves using the addition rule for probabilities and understanding the complement of 'major mental health issues.'
Step 2: Identify the relevant data. From the table, the total number of parents surveyed is 4805. The number of parents who did not have major mental health issues (i.e., those with moderate, minor, or none) is the sum of the values in the 'Moderate,' 'Minor,' and 'None' columns: 1192 + 694 + 2428 = 4314. The number of mothers surveyed is 3661.
Step 3: Use the addition rule for probabilities. The probability of event A (not having major mental health issues) or event B (being a mother) is calculated as P(A or B) = P(A) + P(B) - P(A and B).
Step 4: Calculate P(A), P(B), and P(A and B). P(A) is the probability of not having major mental health issues, which is 4314/4805. P(B) is the probability of being a mother, which is 3661/4805. P(A and B) is the probability of being a mother and not having major mental health issues, which is the sum of the 'Moderate,' 'Minor,' and 'None' values for mothers: (1048 + 514 + 1684)/4805.
Step 5: Substitute the values into the formula P(A or B) = P(A) + P(B) - P(A and B) to find the probability. Simplify the fractions and calculate the result.

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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 involves calculating the chance of selecting a parent who either did not experience major mental health issues or is a mother. This can be determined by dividing the number of favorable outcomes by the total number of outcomes.
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Complementary Events
Complementary events are two outcomes of an event that are mutually exclusive and collectively exhaustive. In this case, the event of a parent not having major mental health issues or being a mother can be analyzed by considering the complementary event, which is a parent having major mental health issues and being a father. Understanding complementary events helps in calculating probabilities more efficiently.
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Conditional Probability
Conditional probability refers to the probability of an event occurring given that another event has already occurred. In this scenario, it may be useful to consider the conditional probabilities of being a mother or not having major mental health issues, as these factors can influence the overall probability calculation. This concept is essential for understanding how different conditions affect the likelihood of outcomes.
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