Appendix B: Statistical Methods
Statistical Methods: Graphing Data
frequency distribution
histogram (basically a bar graph)
frequency polygon
Descriptive Statistics:
measures of central tendency
mean (average)
median (middle)
mode (most)
skewed distributions (when a distribution is symmetrical – it looks the same on both
sides: mean median and mode are all in the same place [bell curve]_
negatively skewed (most data ends up lower of graph: more score is below the mean)
positively skewed (most data ends up upper of graph: more score is above the mean)
measuring variability
standard deviation
**by no means does the mean tell you everything you need to know about the data**
**check out calculating standard deviation**
The Normal Distribution (Bell Curve):
Psychological tests
relative measures
standard deviation is the unit of measure
**50
th
percentile = 50% better than everyone else. 98
th
percentile = 98% better than
everyone else**
Measuring Correlation:
Correlation coefficient
positive = direct relationship **positive doesn’t mean good**  the more of one thing
happens, the more of another thing happens
negative = inverse relationship – if one goes up the other go down
Magnitude: 0 to plus/minus 1 (plus one = perfect positive relationship, zero = no
relationship, minus one = perfect negative relationship)
Scatter diagrams
Correlation of determination
Hypothesis Testing
inferential statistics
sample: has to represent the generalization of the population that you’re applying the
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 Fall '11
 Eibach
 Statistics, Standard Deviation, Manipulate independent variable

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