Pie Graphs, Bar/Column Graphs and X-Y Scatter Plots

A multiple column/bar graph is … …used to show comparisons between two categories. In this case it is types of crime and the year. It is still important to know the whole to which the percentages refer. It is clear here that the whole is all crime since: violent crime (73%) + property crime (27%) = all crime (100%)

Arranging the data for a multiple column/bar chart: One set of categories A second set of categories A blank space Select all of this!

III. x-y scatter plots An x-y scatter plot is a way of graphing data that changes over time An x-y scatter plot is a way of graphing data that changes over time Or, more generally, any data that is of the form (a number, a number). Or, more generally, any data that is of the form (a number, a number). But, in this class, virtually all of the x-y scatter plots you look at will be something that changes over time (abortion rate, population, poverty line, the price of stamps, etc.). But, in this class, virtually all of the x-y scatter plots you look at will be something that changes over time (abortion rate, population, poverty line, the price of stamps, etc.). So, the x-axis will be years, and the y-axis will be the quantity that is changing. So, the x-axis will be years, and the y-axis will be the quantity that is changing. When possible, use relative rather than absolute numbers. When possible, use relative rather than absolute numbers. When labeling the x and y-axis and giving the chart a title, make sure you know the units and the whole to which percents (if you are using percents) refer. When labeling the x and y-axis and giving the chart a title, make sure you know the units and the whole to which percents (if you are using percents) refer.

Here are the violent crime statistics (in thousands) for the United States since 1990: Why is this NOT a very interesting graph? These are total numbers. We don’t know what these numbers mean relative to the population of the U.S..

To fix the problem, get the population for each of these years and then compute: total crimes/total population to get the crime rate. For example: in 1990, (1,820 thousand crimes)/(249,470 thousand people) = OR 703 crimes per 100,000 people Note: All data is in thousands

How might we describe this graph using language? The crime rate is… Increasing Increasing Leveling off Leveling off Decreasing Decreasing Leveling off Leveling off Decreasing Decreasing We might also notice when the highest and lowest points occurred… In there were 758 crimes per 100,000 people In there were 758 crimes per 100,000 people In 2003, there were 475 crimes per 100,000 people In 2003, there were 475 crimes per 100,000 people

Putting this altogether, we could describe the graph as follows: In the early 90’s crime rates were still rising in the United States, but they peaked in 1992 at 758 crimes per 100,000 people. Through the mid to late 90’s there was a decline in the crime rate, bringing it to a low-point of 475 crimes per 100,000 people in But, we may have some cause for concern because although the crime rate has continued to decrease, it seems to have leveled off after the turn of the millennium. The goal in this sort of description is to: 1.) Give a good idea of overall trends, and 2.) Point out the most interesting or surprising features.