Power and Effect Size 21

# Power and Effect Size 21 - Power And Effect Size Types of...

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Power And Effect Size

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Types of Errors Null Hypothesis is REALLY true (treatment does not actually work) Null Hypothesis is REALLY false (treatment does actually work) We DECIDE Null Hypothesis is true (fail to reject null, we decide treatment does not work) We DECIDE Null Hypothesis is false (reject null, we decide treatment does work) Type I Error Type II Error Correct decision Correct decision
Type I Error SCORE -4 -2 0 2 4 0.0 0.1 0.2 0.3 0.4 4 Program Kids SAME as No Program Kids Our sample of Program Kids have scores that are higher than MOST of the population of No Program kids. It looks like there IS a difference between the populations, when actually there is NO difference. We would DECIDE the program works when it actually does NOT work. We would reject the null hypothesis, because the chance that No Program kids would have reading scores this high is 5% or less. The chance of a Type I error is 5% or less. Type I error = p-value

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SCORE -4 -2 0 2 4 0.0 0.1 0.2 0.3 0.4 SCORE -4 -2 0 2 4 No Program Kids Program Kids have higher reading scores than No Program Kids Our sample of Program Kids had scores that are the same as some kids in the population of No Program kids. It looks like there is NO difference between the populations, when actually when actually it does! We would fail to reject the null hypothesis, because the chance that No Program kids would have these reading scores is more than 5%.
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## This note was uploaded on 05/26/2011 for the course PSCH 343 taught by Professor Victoriaharmon during the Spring '11 term at Ill. Chicago.

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Power and Effect Size 21 - Power And Effect Size Types of...

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