The critical value, often represented as a z-score, is the number of standard deviations away from the mean that corresponds to a specific level of confidence in a hypothesis test or confidence interval.
Imagine you are taking a multiple-choice test with 100 questions. You want to know how many questions you need to answer correctly to be in the top 10% of all test-takers. The critical value (z-score) would tell you how many standard deviations above the mean score you need to be in order to achieve that top 10% ranking.
Hypothesis Test: A statistical procedure used to make an inference about a population parameter based on sample data.
Significance Level: The probability threshold below which we reject the null hypothesis in favor of an alternative hypothesis.
One-Tailed Test: A type of hypothesis test where we are only interested in detecting if there is an effect in one direction (either positive or negative).
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