The Three Rules of Data Analysis table of numbers 1 A display of your data will reveal things you are not likely to see in a 2 A well designed display will do much of the work of analyzing you data It can show important features and patterns 3 The best way to report to others what you find in your data is with a well chosen picture Frequency Tables Frequency Table A table that lists the categories in a categorical variable and gives the number the percentage of observations for each category The row percent is the proportion of each row contained in the cell of a frequency table while the column percent is the proportion of each column contained in the cell of a frequency table Relative Frequency Table displays the percentages rather than the counts of the values in each category The Area Principle Area Principle the area occupied by a part of the graph should correspond to the magnitude of the value it represents Bar Charts comparison Pie Charts Pie Charts Contingency Tables Bar Chart Displays the distribution of a categorical variable showing the counts for each category next to each other for easy Relative Frequency Bar Chart replaces the counts with percentages show the whole group of cases as a circle Contingency Table a table that shows how the individuals are distributed along each variable depending on or contingent on the value of the other variable Marginal Distribution In a contingency table the distribution of either variable alone The counts or percentages are the totals found in the margins of the table Each cell of a contingency table gives the count for a combination of values of the two variables Most statistics programs offer a choice of total percent row percent or column percent for contingency tables Conditional Distribution the distribution of a variable restricting the who to consider only a smaller group of individuals Segmented Bar Chart treats each bar as the whole and divides it proportionally into segments corresponding to the percentage in In a contingency table when the distribution of one variable is the same for all categories of another we say that the variables are each group independent Simpson s Paradox A phenomenon that arises when averages or percentages are taken across different groups and these group averages appear to contradict the overall averages
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