UASTAT141Ch21

UASTAT141Ch21 - β = P(H is not rejected | H is false The...

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Ch. 21 - Errors in Hypothesis Testing In any hypothesis test, there is 1 of 2 choices: reject or not reject. There is also 1 of 2 choices as the test applies to reality: H 0 is true or H 0 is false. Actual situation H 0 is true H 0 is false Do not reject H 0 Correct Decision Type II or β error Decision Reject H 0 Type I or α error Correct Decision Def’n: A Type I error occurs when a true null hypothesis is rejected. The value of α represents the prob. of committing this type of error; that is, α = P (H 0 is rejected | H 0 is true) The value of α represents the significance level of the test. A Type II error occurs when a false null hypothesis is not rejected. The value of β represents the prob. of committing a Type II error; that is,
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Unformatted text preview: β = P (H is not rejected | H is false) The value of 1 – β is called the power of the test . It represents the probability of NOT making a Type II error. Example where H : “innocent until proven guilty” Actual situation Innocent Guilty Find not guilty Correct Decision Type II or β error Jury’s decision Find guilty Type I or α error Correct Decision These 2 errors are dependent. For a fixed sample size, lowering α will raise β and vice versa. Decreasing α and β simultaneously requires increasing the sample size. Further information on the errors are not covered in this course....
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• Winter '10
• PaulCartledge
• Null hypothesis, Statistical hypothesis testing, Type I and type II errors, Statistical power, β, α

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