Chapter 14 – Graphical representation of data
This chapter deals with the representation of data sets in charts or graphs.
Exercises
Here is the datafile to be used for a box-plot as referred to in the exercises for this chapter:
Exercise 14.1
A bar chart
Students on an organisational psychology course have taken part in an experiment in which they have first conducted an interview while being observed by a visiting lecturer. Half the students are told the visitor was an expert in human relations and half of this group are given positive feedback by the visitor while the other half are given negative feedback. The other half of the students are told their visiting observer is simply ‘an academic’ and the same two types of feedback are given by the visitor to this group. Students were then asked to rate their own interview performance on a scale of 1 (very poor) to 10 (excellent). The results are displayed in the combined bar chart below.
Please describe the results as accurately as you can (no specific numerical values are required) and offer some possible explanation of the findings.
Show answer
In general positive feedback has greater effect than negative feedback. In addition there appears to be a greater effect from the expert than from the academic. However, there also seems to be an interaction in that the academic’s negative feedback appears to have had a greater lowering effect than that of the expert. Perhaps the students receiving expert negative feedback would rationalise that the expert would be particularly harsh and have therefore discounted some of the feedback.
Exercise 14.2
A histogram
A psychology lecturer has given her students a class test where the maximum mark possible is 50. The histogram above shows the distribution of the test score data. The median of this distribution is 38 and the mean is 37.02.
1. Was the test easy or hard?
Show answer
Easy. The distribution is negatively skewed and shows a ‘ceiling effect’ with many scores near the top end of the scale.
2. Why is the mean lower than the median?
Show answer
Because the distribution is negatively skewed and therefore there are more extreme low scores in the tail pulling the mean (37.02) lower than the median (38).
3. What is the modal category of scores?
Show answer
38–40
Note: The data for this histogram are contained in the file Psychology test scores.sav used in the Chapter 13 exercises.
Weblinks
Graphical representation of data
Some chart making online apps:
Online Chart and Graph Maker – Chartle.com