Chapter 2 - Displaying Data with Graphs

distribution

tells us what values a variable takes on how often it takes each value

frequency table

shows the number of individuals having each data value

relative frequency table

shows the proportion or percentage of individuals having each data value

bar chart

shows each category as a bar, the heights of the bars show the category frequencies or relative frequencies

pie chart

shows each category as a sector of a circle, the areas of the sectors are proportional to the category frequencies or relative frequencies

two-way table

a table of frequencies that summarizes the relationship between two categorical variables for some group of individuals

side-by-side

displays the distribution of a categorical variable for each value of a categorical variable, where bares are grouped together based on the values of one of the categorical variables and placed next to each other.

segmented bar-chart

displays the distribution of a categorical variable as portions of a rectangle, with the area of each segment proportional to the percentage of individuals in the corresponding category.

association

a property between two variables if knowing the value of one variable helps us predict the value of the other, this must be the case for there to be association.

dotplot

shows each data value as a dot above its location on a number line

roughly symmetric

a quantitative distribution in which the right side of a graph is approximately a mirror image of the left side.

skewed to the left/right

a dotplot with a distribution where the right/left side of the graph is much longer than the left/right side. (“skiing” down the slope in the direction of skewness)

stemplot

shows each data value separated into two parts: a stem, which consists of the leftmost digit(s), and a leaf, the final digit. The stems are ordered from least to greatest and arranged in a vertical column. The leaves are arranged in increasing order out from the stems.

histogram

shows each interval as a bar, the heights of the bars show the frequencies or relative frequencies of values in each interval

scatterplot

shows the relationship between two variables measured on the same individuals. the values of one variable appear on the horizontal axis, and the values of the other variable appear on the vertical axis, each individual data ser appears as a point on the graph