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Learning Math Home
Data Session 7, Part A: Scatter Plots
 
Session 7 Part A Part B Part C Part D Homework
 
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Session 7 Materials:
Notes
Solutions
Video

Session 7, Part A:
Scatter Plots

In This Part: A Bivariate Data Question | Building a Scatter Plot | A Further Question
Quadrants

Analyze the Data
We will now begin our analysis of the bivariate data and explore the co-variation in the arm span and height data. Here again are the collected arm spans and heights for 24 people, sorted in increasing order by arm span:

Person #

Arm Span

Height

1

156

162

2

157

160

3

159

162

4

160

155

5

161

160

6

161

162

7

162

170

8

165

166

9

170

170

10

170

167

11

173

185

12

173

176

 

Person #

Arm Span

Height

13

177

173

14

177

176

15

178

178

16

184

180

17

188

188

18

188

187

19

188

182

20

188

181

21

188

192

22

194

193

23

196

184

24

200

186

Bivariate data analysis employs a special "X-Y" coordinate plot of the data that allows you to visualize the simultaneous changes taking place in two variables. This type of plot is called a scatter plot. Note 1

For our data, we will assign the X and Y variables as follows:

X = Arm Span
Y = Height

To see how this works, let's examine the 10th person in the data table. Here are the measurements for Person 10:

X = Arm Span = 170 and Y = Height = 167

Person 10 is represented by the coordinate pair (170, 167) and is represented in the scatter plot as this point:

Scatter for 1

Let's add two more points to the scatter plot, corresponding to Persons 2 and 23:

Person #

Arm Span

Height

2

157

160

23

196

184

Scatter for above table

Here is the completed scatter plot for all 24 people:

Scatter for all 24

Problem A3

Solution  

Judging from the scatter plot, does there appear to be a positive association between arm span and height? That is, does an increase in arm span generally lead to an increase in height?



video thumbnail
 

Video Segment
In this video segment, Professor Kader introduces bivariate analysis. The participants measure their heights and arm spans and then create a scatter plot of the data. Professor Kader then asks them to analyze the association between the two variables, height and arm span.

If you're using a VCR, you can find this segment on the session video approximately 4 minutes and 34 seconds after the Annenberg Media logo.

 

 
 

The scatter plots illustrate the general nature of the association between arm span and height. Reading from left to right on the horizontal scale, you can observe that narrow arm spans tend to be associated with people who are shorter, and wider arm spans tend to be associated with people who are taller -- that is, there appears to be an overall positive association between arm span and height.


Next > Part A (Continued): A Further Question

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