#### Do you want to… analyze categorical data in one dimension?

*Stephan is collecting data on vehicle ownership by household and breaks respondents into 4 groups: no vehicles, one vehicle, two vehicles, and 3 or more vehicles…*

### Bar graphs vs Histograms

#### Confusion often exists on the difference between a bar graph and a histogram. Histograms have previously been shown as a useful tool to demonstrate frequency among data points which are quantitative – showing the shape of a distribution visually. Bar graphs cannot convey distribution shape as they show frequency among *categories*. The order in which those categories are placed on the x-axis is not predetermined – they can be arranged in any order. This means the shape of the bars produced is irrelevant.

#### This first video uses this flower model to demonstrate how to construct a bar graph in Excel.

#### This second video demonstrates how to use Excel to create scatterplots as well as bar graphs.

#### Do you want to… analyze categorical data in two dimensions?

*Catherine is doing her science fair project on smoking prevalence (have never smoked, former smoker, currently smoke) among different age groups (30 and younger, 30 to 50, and older than 50) in San Joaquin county. She interviews 100 random individuals asking them their age and smoking habits…*

### Two Way Tables

#### Two way tables are powerful for conveying information about categorical data in two dimensional space but conclusions from that data should be carefully considered. This video will demonstrate the process of creating two way tables and will illustrate some cautions with their use.

#### This first video uses this new flower model to demonstrate how to construct two way tables and two dimensional bar graphs in Excel, producing this document.

#### This second video demonstrates how to use Excel to create scatterplots as well as bar graphs.

### Chi Squared Testing

#### Chi Squared tests are used to determine if there is a significant difference among the categories in a two way table or bar graph.

#### This video was produced by Marcus Sherman and explains the Chi-Squared test – thanks Mr. Sherman!

#### This video is a crash course in Chi Squared, explaining what it is and how to calculate it.