Conducting ANOVAs in SPSS

# Conducting ANOVAs in SPSS - PSYC3000 Experimental Methods...

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Page 1 of 5 Analysis of Variance One-Way ANOVA What it does The one-way analysis of variance (ANOVA) is used to determine whether or not the dependent variable has the same population mean in each of several different groups. The independent variable is used to indicate the group to which each participant belongs. Using SPSS to obtain the descriptive statistics for the one-way ANOVA 1) From the Analyze menu, select Compare Means , and then Means… . 2) Move the dependent variable into the Dependent List box. 3) Move the independent variable (the variable that indicates in which group each participant belongs) into the Independent List box, then click on OK . Running the one-way ANOVA in SPSS 4) The independent variable (IV) is used to indicate group membership. Skip to Step 8 if the IV is a numeric variable . Otherwise, make the data grid the active window. 5) Select the Automatic Recode procedure from the Transform menu. This procedure is used to automatically convert string variables (which SPSS cannot use in ANOVAs) into numeric variables. 6) Move the independent variable into the Variable -> New Name box. 7) In the small box to the right of New Name , enter the name that SPSS should use for the numeric variable it will create for the IV. Then, click on New Name , and click on OK . 8) From the Analyze menu, select Compare Means , and then One-Way ANOVA… . 9) Move the dependent variable into the Dependent List box. 10) Move the IV into the Factor box, then click on OK . Interpreting the SPSS output First, examine the descriptive statistics (M, n , and SD) for each group, as output by the Means procedure. If the samples means for each group are fairly similar to each other, the corresponding population means are probably identical to each other. However, if the sample means differ markedly from each other, this could signify that the population means also differ from each other. To determine which conclusion to draw, examine the output from the One-Way ANOVA procedure, and in particular the p-value for the ANOVA, which is labeled “Sig.” If p is greater than .05, the result is not statistically significant, and you should conclude that all groups share the same population mean for the dependent variable. However, if p is less than or equal to .05, you have a significant result and the population mean of at least one group differs from the population mean of the other groups. If you have a significant result, you must determine its direction. Look again at the sample means for each group. Groups that have markedly different sample means are also likely to have different population means, while groups with similar sample means probably have identical population means. Try to determine which groups have the largest means, and which groups have the smallest means.

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Page 2 of 5 Reporting results in APA format 1) If you had a non-significant result, begin with this sentence: [ Description of dependent variable
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## Conducting ANOVAs in SPSS - PSYC3000 Experimental Methods...

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