Lecture 2.2 - Describing Categorical Data - Charts of categorical data

Question 1

Charts of categorical data

Answer 1

1. Bar chart and pie chart are common displays for a categorical variable.
2. Both summarize the variable using its frequency table.

Question 2

Pie charts

Answer 2

1. A pie chart is a circular graph that represents the relative frequencies of different categories in a qualitative data set.
2. The size of each slice is proportional to the relative frequency of its corresponding category. The slices are labeled with the category names and their relative frequencies.

Question 3

Pie chart in a google sheet

Answer 3

1. Highlight data to visualize
2. Click “Insert Chart” in toolbar
3. Open chart editor and select “Pie chart” type.

Question 4

Bar chart

Answer 4

1. Bar chart: displays distinct values of qualitative data on a horizontal axis and relative frequencies on a vertical axis.
2. Each distinct value is represented by a vertical bar whose height is equal to its frequency/relative frequency.
3. Bars should be positioned apart so they don’t touch.

Question 5

Steps to construct a Bar Chart

Answer 5

1. Get frequency/relative frequency distribution of data
2. Draw horizontal axis for values, vertical axis for frequency/relative frequency
3. Construct bars for each value with height equal to frequency/relative frequency
4. Label bars with values, horizontal axis with variable name, vertical axis with “Frequency”/ “Relative frequency”.

Question 6

Pie chart in a google sheet

Answer 6

1. Highlight/select data to visualize.
2. Click “Insert Chart” in Google Sheets toolbar.
3. Change chart type in Chart Editor.
4. Select “Bar Chart” in Chart Editor.

Question 7

Pareto Charts

Answer 7

1. Bar chart sorted by frequency is a Pareto chart, used for quality control.
2. Bar chart for an ordinal variable must preserve the ordering.