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Data Session 6, Part C: Comparative Experimental Studies
 
Session 6 Part A Part B Part C Homework
 
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Session 6, Part C:
Comparative Experimental Studies

In This Part: Measuring Short-Term Recall | An Experiment | Experimental Design
Analysis of the Experiment

Analyze
Sixteen subjects participated in the memory experiment using Design 5. Eight subjects were randomly assigned to each group. Each subject in Group 1 was first measured using List A. Then each subject in Group 1 was measured using List B. The order was reversed for Group 2: The subjects were first measured using List B, then List A. Here are the measurements from the experiment:

Number Recalled Correctly

Person

List A:
Words

List B: Non-Words

Difference

1

12

9

3

2

15

6

9

3

12

5

7

4

12

4

8

5

10

5

5

6

3

5

-2

7

7

5

2

8

11

2

9

9

9

1

8

10

14

8

6

11

9

1

8

12

10

5

5

13

9

6

3

14

5

4

1

15

13

9

4

16

10

4

6

Because every subject was measured using both List A and List B, it is of interest to look at the differences in the subjects' scores (Score A - Score B), which are shown in the last column.

Problem C7

Solution  

a. 

Determine the Five-Number Summary for the 16 scores using List A.

b. 

Determine the Five-Number Summary for the 16 scores using List B.

c. 

Using the same scale, sketch the two box plots for List A and List B side by side.

d. 

Based on the summaries and box plots, how do scores using List A compare with scores using List B?


 
 

The comparison of the two box plots indicates that the scores of subjects using List A tend to be higher than the scores of subjects using List B; therefore, subjects recalled words more readily than they recalled non-words. The difference in the two medians (10 - 5 = 5) indicates that people can typically recall five more words than non-words. However, there is somewhat more variation in the scores from List A (words) than from List B (non-words); the range for List A is 12 compared to 8 for List B, and the IQR for List A is 3 compared to 2 for List B.



video thumbnail
 

Video Segment
In this video segment, Professor Kader and participants display the results of the study on short-term recall on box plots and discuss what they see. Watch this segment after completing Problem C7.

Why are box plots helpful in studying the results of comparative experiments?

If you're using a VCR, you can find this segment on the session video approximately 16 minutes and 15 seconds after the Annenberg Media logo.

 

 
 

This comparative analysis does not take into account the advantage you gain from pairing each subject's scores from both lists and then examining the difference between the two scores (Score A - Score B). A positive difference occurs when the List A score is higher than the List B score; that is, the difference is positive when memory recall is better for words than for non-words. Note 7


 

Problem C8

Solution  

Examine the column of differences in the Number Recalled Correctly table:

a. 

How many of the differences are positive? How many are negative?

b. 

What does this suggest about memory recall of words versus non-words?

c. 

Determine the Five-Number Summary of the 16 differences.

d. 

Sketch the box plot of the differences.

e. 

Based on the Five-Number Summary and box plot of the differences in scores between the two lists, how do scores using List A compare with scores using List B?


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