PS295 Chapter Notes -Effect Size, Type I And Type Ii Errors, Null Hypothesis
Document Summary
If the iv has an effect on the dv we should find that the means for the experimental conditions differ. Different group averages would suggest that the iv had an effect; it created differences in the behaviour in various conditions and resulted in systematic variance. Problem: means of experimental conditions may differ even if the iv does not have an effect. Error variance reflects the random influences of variables that remain unidentified in the study. These uncontrolled and unidentified variables lead participants to respond differently whether or not the iv has an effect. If we can estimate how much the means of the conditions are expected to differ even if the iv has no effect, then we can determine whether the difference we observe between the means exceeds this estimate. Researchers use inferential statistics to determine whether observed differences between the means of the experimental conditions are greater than expected on the basis of error variance alone.
