BUS 264 - Chapter 4

Three rules of data analysis

Rules 1, 2, 3: MAKE A PICTURE!Pictures:-reveal things that can't be seen in a table of numbers.-show important features and patterns in the data.-provide an excellent means for reporting findings to others.

Frequency Table

A Frequency table organizes data by recording totals and category names.-names are in the rows-quantitative data in the columns

Relative Frequency Table

A relative frequency table displays the percentages that lie in each category rather than the counts.

Area Principle

Figures that distorts the data from the frequency tables. (overemphasizing one figure in favor of another)The best data displays observe the area principle: the area occupied by a part of the graph should correspond to the magnitude of the value it represents.

Bar Charts

A bar chart displays the distribution of a categorical variable, showing the counts for each category next to the each other for easy comparison.

Relative Frequency Bar Chart

If the counts are replaced with percentages, the data can be displayed in a relative frequency bar chart.

Pie Charts

Pie charts show the whole group of cases as a circle sliced into pieces with sizes proportional to the fraction of the whole in each category.

Categorical Data Condition

The data are counts of percentages of individuals in categories.

Contingency Table

A frequency table in which smaller categories are added as a new variable.

Marginal Distribution

The marginal distribution of a variable in a contingency table is the total count that occurs when the value of that variable is held constant.


Each cell of a contingency table (any intersection of a row and column of the table) gives the count for a combination of values of the two variables.

Conditional Distribution

To restrict variables in ad distribution to show the distribution for just those cases that satisfy a specified condition.


In a contingency table, when the distribution of one variable is the same for all categories of another variable, we say that the variables are independent.

Segmented Bar Chart

Data can be displayed by dividing up bars rather then circles. A chart where a bar is divided proportionally into segments corresponding to the percentage in each group.

Simpson's Paradox

Percentages that are inappropriately combined.