Summary: Management Research Methods 2
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1 ANOVA
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When can one use ANOVA?
 The OV is quantitative
 The PV is categorical, so has two or more categories (0,2 or 4 beers predict if something will happen)
 participants differ from each other (different test groups do not have the same participants)
 population is normally distributed
 populations must have the same variance 
Variance testing can distinguish two tests, which two?
Variance testing within groups
Variance testing between groups (this is the one that says the most) 
What does the Ftest tell (ANOVA)?
Variance between sample means / variance within the samples
Variance between sample means = mean sum of squares of the model / Degrees of Freedom (number of groups  1)
Variance within the samples = Mean square residuals / Degrees of Freedom (number of participants  number of groups) 
When is there effect from a PV on an OV?
When the explained variance (between groups) is large relative to the unexplained variance (within groups) > High F score 
What is a BrownForsyth or Welch test?
It is a criterion that tells if ANOVA can be done P > 0.05 
What happens with R2 when there is only one PV?
Than R2 becomes eta2 
A Ttest cannot be done to test for statistical evidence because there are used more than 2 groups to test (3x40N). Why can one not do multiple ttests on these groups to find evidence?
Because of alpha inflation (type 1 error)
To test with 3 groups, three ttests have to be done.
10.95 = 0.05
10.95^3 = 0.14 
What are the two criteria for planned contrast tets?
1. Sum of the weights must be 0
2. If multiple contrasts are done (so multiple hypotheses are tested) they must be orthogonal. This means that the multiplied comparison of the tetst must be 0.
Example: H1 = group 2 > group 3 > 0, 1, 1
H2 = group 1 > rest > 1, 0.5, 0,5
multiplied comparison:
0*1 = 0
1*0.5 = 0,5
1*0.5 = 0.5
These added up is 0, so they are orthogonal! 
What does the Levene probability tell?
If the significance is >0.05, than equal variances can be assumed. 
What is a post hoc test?
Statistical test afterwards to check the reliability of the earlier tetst done.
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