Lab 4 Summary Statistics & Graphing Quantitative Data (Box Plots)

Math 134 Lab 4

Summary Statistics & Graphing Quantitative Data (Box Plots)

The purpose of this lab is to teach you how to get summary statistics and graph quantitative data with a box plot. We will make graphs using data from “State Data 2009-2010” found on our class group data. Open the data file and read the description of the data set’s variables.

Step 1. Make a box plot. Select Graphics/Boxplot. Select “Crime” as your column.

Click next and select “Draw boxes horizontally” and “Use fences to identify outliers”.

Click next and type in an appropriate label for the X axis and a great Title for your graph. Remember Who, What, Where. When. Include if the graph uses all data or if an outlier was removed.

Select “Create Graph”

Export your results. Print in color.

Step 2. Get summary stats for “Crime”. Select Stats/Summary Stats/ Columns.

Select “Crime”

Click next. There should be a preselected list. Make sure the list includes mean, standard deviation, min, Q1, median, Q3, max and IQR. Add any that are not already selected and remove those that are extra.

Select “Calculate”

Export your results. Use Edit in the results to change the title to indicate if this output uses all the data or if an outlier was removed and print.

Step 3. Remove the outlier in “Crime” (make a note of where it comes from) and repeat steps 1 & 2

Step 4. Repeat Step 1 & 2 for the variable “Metro”, be sure to use the ENTIRE data set.

Discussion questions:

1. Please indicate the placement of the mean on each boxplot with AND without the outlier for Crime and for Metro. (You’re right, this is not a question.) 

2. Is the outlier in the data for Crime influential? Explain why it is or why it is not.

3. Would you use the output with all the data or without the outlier to describe Crime in the US? Explain your choice.

4. Based on what you decided in question 2, use your box plot and the summary statistics to describe the distribution of the variable “Crime”. What does this tell us about the United States’ level of crime in general?

5. Describe the distribution of the variable “Metro”. Use your box plot and the summary statistics. What does this tell us about the United States in general? Are we an urban or more rural society?

Lab 4 will have as computer output three box plots (printed in color) and three sets of summary statistics.