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.
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.
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.
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 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.
A frequency table in which smaller categories are added as a new variable.
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.
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.
Percentages that are inappropriately combined.