QTM 100 CH 2

Contingency Table

Table that summarizes data for two categorical variables

Stacked bar plot

Graphical display of contingency table information, compare sto variables on top of each other *not added

Side by side bar plot

Compares two variables side by side

When is stacked, side by side, or standardized stacked bar plot the most useful?

Stacked bar plot: assign one variable as explanatory and other as response

Side by side: does not show which variable causes the other, easy to compare cases but requires more horizontal space, also not favorable if groups are different sizes

Standardized bar plot: used if primary variable is relatively imbalanced, shows proportions

Mosaic plot

Resembles standardized stacked bar lot

(Widths = proportions)

Use areas to represent number of cases in each category

Side by side plot

Traditional tool for comparing across groups

Hollow histograms

Compare numerical data across groups (shown with outline)

Hollow histograms vs side by side plots

Hollow histograms: useful for seeing distribution and skew

Side by side boxplots: useful for comparing centers and spreads

Scatterplot

Case by case data for two numerical variables

Dot plot

One variable scatterplot

Formula for end of whiskers

Q1-1.5 times IQR or Q3+1.5 times IQR