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Chapter 7 - Analysing the Data Part IV - Analysis of Variance Chapter 1 - Behavioural Science and research Chapter 2 - Research Design Chapter 3 - Collecting the Data Chapter 4 - Analysing the Data Part I - Descriptive Statistics Chapter 5 - Analysing the Data Part II - Inferential Statistics Chapter 6 - Analysing the Data Part III - Common Statistical Tests


Chapter 7: Analysing the Data
Part IV : Analysis of Variance


Scenario and Data Set #2
SPSS Instructions

  1. Enter these data into SPSS and save the data as a file.
    Note: The way in which the data for this problem is entered into SPSS is not the same as it is displayed in the table provided (see Figure 7.3 below).

  2. Run the 'Compare Means' procedure with the appropriate options.

  3. Conduct a post hoc analysis (Tukey's HSD) on these data.

  4. Graph results using a bar graph.


Figure 7.2 Format of data entry

Notice two columns only. One for the Grouping variable (IV) and one for the Test variable (DV). There are 50 lines of data, one line per case (i.e., thing being measured in this situation, people).

Figure 7.3 Where to find One-way between groups ANOVA.

Figure 7.4 Defining dependent and independent variables.

Notice that the Dependent variable is recall and the Factor is group. Notice, also that the set up for this procedure allows you to run several one-way between group ANOVAs, just by specifying several DVs in the above box. If you did nominate 3 DVs, you would be running 3 separate ANOVAs, each at alpha = .05. You should therefore use a Bonferroni adjustment on the alpha -level. In this case, you would only declare a significant finding if the 'Sig.' value for the F-ratio was < .0167.

Figure 7.5. Options for the One-way Between groups ANOVA.
Descriptive, Homogeneity of variance and Means plot.

Figure 7.6. Post hoc options

Notice that there are several options here depending on whether "Equal Variances Assumed" or "Equal Variances Not Assumed". Initially, you should assume the variances are equal (most often the case). If the diagnostics in the SPSS output show that this assumption is untenable, you should re-run the analysis, this time checking one of the "Equal Variances Not Assumed" options. The "Games-Howell" option is recommended in this situation.




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