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By the end of this workshop you will be able to:
Illustrative statistics are used to summarise data in a similar manner to descriptive statistics. Summarising data in a graph can be more meaningful to the reader rather than merely reporting descriptive statistics in a table. In a graph the main features of the data and any patterns can be clearly seen. Illustrative statistics can also facilitate statistical judgement.
Bar charts can be used to describe a discrete data set or to compare two discrete data sets.
N.B. The quantity on the horizontal axis of a bar chart must be discrete.
Load the data file ‘dataset1 from the server data files to get the data sheet below
Obtaining Bar Charts through the Frequency Command
Pie charts can be used to describe a discrete non-numerical data set.
N.B. A pie chart is meaningless unless the complete pie represents the sum of the separate parts.
To obtain the descriptive statistics for the illustrative data set 1 and illustrate with a pie chart (again using the Frequencies command but select Pie chart when in the Charts dialogue box). That is, use the same procedure as used for frequency-given bar charts but instead select Pie Chart.
Histograms can be used to describe the spread of values within a variable that contains numerical continuous data. Histograms illustrate frequency data presenting the distribution of data within the variable.
Load the data file ‘dataset1 from the server data files and follow the procedure below.
The Histogram Output
The y-axis represents the number of occurrences in which each ghq score was noted in the data sheet.
N.B. Again, you can use the Analyze, Descriptive Statistics, Frequencies, Charts procedure. Alternatively you can go to the Graphs pull down menu and select Histogram (however, this procedure only allows you to select one variable at a time).
Boxplots visually display several main features of the data. Boxplots are often used to compare the distributions of two data sets.
A boxplot is a method of representing some of the main features of a set of data.
The boxplot indicates the range of the raw data and the distribution of scores for men and women’s ghq scores.
From this boxplot, male participants had more similar scores than females. The median is where we cut our list of scores in to two halves. Therefore spread of male ghq was predominantly at a lower level than for females
Task:
Produce a boxplot for age by bmi or produce a boxplot and stem and leaf plot for BMI and GHQ for illustrative data set 2.
To produce descriptive statistics, stem and leaf plot and boxplots for BMI by gender and then by age and the same for GHQ.
(The procedure is similar to that above. The only difference being that Gender and Age need to go into the Factor List box.)
After creating illustrative statistics in SPSS you are often required to import the graph into a Microsoft Word document. The procedure for this is quite simple. However, SPSS only allows you to import one frame at a time, i.e. only one chart at a time.
N.B. You can now modify the graph if you wish (i.e. the size).
Apply» Faculties & Departments» Department of Psychology» Labs» SPSS statistical procedures» Illustrative Statistics
