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 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
4. Probability
Basic Concepts of Probability
Problem 3.1.9
Textbook Question
True or False? In Exercises 7-10, determine whether the statement is true or false. If it is false, rewrite it as a true statement.
9. A probability of 1/10 indicates an unusual event.

1
Step 1: Understand the concept of an 'unusual event' in probability. In statistics, an event is typically considered unusual if its probability is less than or equal to 0.05 (5%). This threshold is commonly used but can vary depending on context.
Step 2: Convert the given probability of 1/10 into decimal form for easier comparison. The probability 1/10 is equivalent to 0.1 (10%).
Step 3: Compare the probability of 0.1 to the threshold of 0.05. Since 0.1 is greater than 0.05, the event is not considered unusual based on the standard threshold.
Step 4: Rewrite the statement if it is false. The correct statement would be: 'A probability of 1/10 does not indicate an unusual event.'
Step 5: Conclude the reasoning by emphasizing that the classification of an event as unusual depends on the probability threshold, which is typically 0.05 in most statistical contexts.

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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 a particular event will occur, expressed as a number between 0 and 1. A probability of 0 indicates that an event will not happen, while a probability of 1 indicates certainty. Probabilities can also be expressed as fractions, percentages, or decimals, and they help in assessing the risk and making informed decisions.
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Unusual Events
An unusual event is typically defined as one that has a low probability of occurring. In many contexts, events with probabilities less than 0.05 (or 5%) are considered unusual. However, the threshold for what constitutes 'unusual' can vary depending on the specific context and the norms of the field of study.
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Interpreting Probability Values
Interpreting probability values involves understanding what different probabilities signify about the likelihood of events. A probability of 1/10 (or 0.1) suggests that the event is not very likely to occur, but it is not necessarily unusual. This interpretation is crucial for accurately assessing statements about events and their probabilities.
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