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QM #5 Exploring Assumptions (Skewness (:bulb: Unsymmetrical distribution,…
QM #5
Exploring Assumptions
Homogeneity of Variance
:bulb: homogeneous
Measured using Levene's test
Residual
:bulb: The difference between the observed value of the dependent variable (y) and the predicted value (ŷ)
Skewness
:bulb: Unsymmetrical distribution
:heavy_minus_sign:: Distribution tail on the
right
:heavy_plus_sign:: Distribution tail on the
left
"N" > Whole sample
"n" > subsample within the whole sample
probability-probability plot (P-P plot)
quantile-quantile plot (Q-Q plot)
:bulb: a graphical technique for determining if two data sets come from populations with a common distribution. A q-q plot is a plot of the quantiles of the first data set against the quantiles of the second data set.
Type of data
Categorical
Ordinal (order)
:memo: Age group, etc.
Bar chart only
Nominal (arbitrary)
:memo: Gender, marital status, etc.
Bar or pie chart
Scale
:memo: Likert scale questions (see Larson Hall, p. 53)
Outliers
Detecting and dealing with outliers