Chapter 3 1
Two main points of course:
1. Statistical significance – how likely was the data due to the actual manipulation
2. Predictability through an analysis of variability
If statistical significance was <5%, it is most likely due to
“cheating” – difference hypothesis
Statistical significance = how much the standard
score deviates from the mean
Z score – how far away from the mean you are in units of SD
What would the probability of someone having 2 standard deviations? 48% Chapter 3 2
What is the probability of someone having an IQ between 85 and 130? 82% (34% + 34% + 14% = 82%)
What would your IQ be if the Z score was +2? 130. What would your IQ be if the Z score was -1? 85.
(SD units)(SD) + M = value
Z Table on page 671-674:
Example for table: what is the probability of having an IQ of Z =
1.66 or more?
When it is a decimal, it will be for standard deviation.