Inferential Statistics - Statistics and Measurement in Physical Education - Lecture Slides, Slides of Statistics

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Inferential Statistics

Significance Testing

Important Terms

• Null hypothesis
• Significance
• Probability of error (alpha levels)
• Confidence level
• Independent t test
• Dependent t test

Comparing Mean Values

• Mean values will be different
• Caused by chance or caused by IV

Null Hypothesis

• Any observable difference between two mean values is simply due to chance
• Significance testing either accepts or rejects null hypothesis
• Acceptance means that observable difference was due to chance
• Rejection means the IV caused the change

Independent t-test

• To determine significance between two independent groups, i.e., experimental group and control group
• Experimental group receives IV; control group does not
• Was the difference between experimental group mean and control group great enough to state significance?

Significance

• In essence, what is the likelihood that the group that receives the IV will score higher than the group who does not?
• In essence, what is the probability that the group who receives the IV will not score higher than the group who does not?
• In essence, how confident are you that the group who receives the IV will score higher than the group who does not?

Alpha levels (cont.)

• An alpha level of .01 means that less than 1 out of 100 times the IV group might not score higher
• Or, 99% of the times the IV group will score higher
• What about an alpha level of .001?

Non independent t-test

• To determine significance between pre and post tests within one group
• One group, two treatments
• Examples