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15 Cards in this Set
- Front
- Back
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What is probability?
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How often an event occurs compared to how often it could occur
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What is the normal curve?
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A family of unimodal, symmetrical, bell-shaped curves that correspond to the frequencies of many phenomena.
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What is the relationship between probability and the normal curve?
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The total area under the normal curve equals the probability of all possible outcomes.
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Approximately what percent of cases fall between the mean and one standard deviation above the mean in a normal distribution?
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34%
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Approximately what percent of cases fall between one and two standard deviations above the mean in a normal distribution?
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14%
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Approximately what percent of cases fall more than two standard deviations above the mean in a normal distribution?
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2%
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What percent of cases fall above the mean in a normal distribution?
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50%
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What is a population?
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All cases in which you are interested
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What is a sample?
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A subset of cases taken from a population
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What is a non-probability sample?
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A sample that does not rely on mathematical randomness to determine which cases are included.
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What is a probability sample?
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A sample that relies on mathematically random selection to determine which cases are included.
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What is a parameter?
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The value of a characteristic in a population (usually unknown/unknowable)
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What is a statistic?
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An estimate of a population parameter based on sample data
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When finding the percent of cases above or below a z-score, add 50% to the percent you look up in table A-1 if you're looking for...
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1. ...the percentage of cases above a negative z-score.
2. ...the percentage of cases below a positive z-score. |
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How do you calculate a probability?
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Divide the number of "successful" outcomes (i.e., those that meet your defined criteria) by the total number of possible outcomes.
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