Handbook Statistics for Premasters

Handbook Statistics

Contents
Some important things.......................................................................................................................3
Measurement levels.......................................................................................................................3
Read histogram...............................................................................................................................3
Read boxplot...................................................................................................................................3
Read scatterplot.............................................................................................................................4
Read bar chart................................................................................................................................4
Reporting rules...............................................................................................................................4
Choose the right test..........................................................................................................................6
One-sample t-test...............................................................................................................................9
Steps...............................................................................................................................................9
Reporting......................................................................................................................................10
Independent t-test............................................................................................................................12
Steps.............................................................................................................................................12
Reporting......................................................................................................................................14
Dependent (paired sample) t-test....................................................................................................16
Steps.............................................................................................................................................16
Reporting......................................................................................................................................18
One-way ANOVA...............................................................................................................................19
Steps.............................................................................................................................................19
Reporting......................................................................................................................................22
Factorial (two-way) ANOVA..............................................................................................................25
Steps.............................................................................................................................................25
Reporting......................................................................................................................................29
Correlation........................................................................................................................................32
Steps.............................................................................................................................................32
Reporting......................................................................................................................................34
Regression........................................................................................................................................38
Steps.............................................................................................................................................38
Reporting......................................................................................................................................39
Chi-square........................................................................................................................................42
Steps.............................................................................................................................................42
Reporting......................................................................................................................................44

,Drawing conclusions.........................................................................................................................46
Definitions........................................................................................................................................47
 Remember that a complete answer contains several different elements:
 Rephrasing the H
 Indicating the test
 Means, SD’s
 When scale is involved: Cronbach alpha, + information about the
questions
 Assumptions (when violated)
 The test
 Effect size
 Conclusion

, Some important things

WATCH OUT: When using bootstrap or split file, always remove it afterwards!

Measurement levels




SPSS




Read histogram
Simple histogram shows frequencies of scores for a single variable.

Skewness and kurtosis




Negatively skewed. Positively skewed. Skewed
Skewed to the left: the tale to the right: the tails points
pints to the left. to the right.




Negative kurtosis. Positive kurtosis.
Platykurtic distribution: Leptokurtic distribution:
Flat (with no tales). High peak.

Read boxplot
- Skewness and kurtosis: When the sides are not symmetrical, it is skewed.
- Intervals: When confidence intervals of different samples overlap, it means
they can come from the same population, means can be the same.