Spss For Oneway Anova

SPSS for Oneway ANOVA Example: Problem 23, p. 376 Are non-migrating birds more intelligent? Homework: Problems 15 (p. 375) and 25 (p. 377) Include a box plot for each problem. Use APA format (italics,Greek letters, superscripts) in write-up. Staple ALL the pages into one packet with your name on it.

Data as shown in the book “ One possible explanation for why some birds migrate and others maintain year round residence is intelligence. Birds with small brains (relative to their body size) are simply no smart enough to find food during the winter. … The numbers represent relative brain size for the individual birds in the sample.” 3 16 16 14 6 23 2 16 17 4 7 11 2 5 8 Long Distance Short Distance Non-Migrating

The data
Grouping variable (Factors)
Bird Migration Pattern
Non-Migrating
Short-Distance Migrants
Long-Distance Migrants
Dependent Variable
Relative brain size of individual birds

Variable View in SPSS Two variables defined: BrainSize - the actual numbers shown in the data in the book Migration - the bird’s group, shown by columns in the data

Variable View - Values Add labels to the Factor (Grouping) variable by clicking on the gray box under Values. Use the code 1=Non-Migrating, 2=Short Distance and 3=Long Distance

Data View in SPSS Type in the codes for migration: 5 codes of “1”, of “2” and of “3” Then type in the BrainSize data, matched to the code for the right kind of bird (1=Non-Migrating, etc.) Before going further: SAVE AS … go to your K: drive save as Q13-23.sav If something goes wrong, you will still have your data available.

Look at a boxplot to visualize the relationships you are testing Graphs Legacy Dialogs -> Boxplot … . a dialog box opens Choose “Simple” and “Summaries of groups of cases” then DEFINE.

Boxplot (color added) Notice that the value labels show up in good format for the chart (less need to edit). Notice that the variability within groups differs, and that the central tendency (median) differs. Note the outlier.

Oneway ANOVA in SPSS Analyze -> Compare Means -> One-Way ANOVA a dialog box will open

Dialogues
Put grouping variable (independent) into the FACTOR box
Put continuous variable (dependent) into the DEPENDENT box
Click on Options …
Choose Descriptives
Click Continue …
Click Post Hoc

… Post Hoc If groups are all the same size: select TUKEY If groups are different sizes: select SCHEFFE Then click Continue … Finally, Click OK.

OUTPUT has many parts Look at sig. for hypothesis test: If Sig < α Reject H 0 Here, Sig = .042 Sig < .05 so Reject H 0 EFFECT SIZE

Output (continued) The Multiple Comparison output (Tukey HSD) compares the means of the dependent variable for each combination of Factor categories. An * indicates a significant difference ( p < .05). Here, the relative brain size of the non-migrating birds differed significantly from the long-distance migrators; no other differences were significant.

Write-Up: Format
The Sandwich format still applies
An opening that describes the data
Sentences that present the results
Must include decision (significant or not)
Must include F and p
If significant, must include Post-Hoc tests
If significant, must include Effect Size ( η 2 )
If significant, should include M , SD at least for groups that differ significantly on post hoc tests
Closing summary sentence

Write Up Researchers tested the hypothesis that differences in birds’ intelligence, measured by the size of their brain relative to their body, is related to their pattern of migration. Differences were observed in the relative brain sizes of non-migrating birds ( M = 15.00, SD = 5.788), those that migrate short distances ( M = 10.00, SD = 5.523), and that migrate long distances ( M = 5.00, SD = 5.099); the differences were significant ( F 2,12 = 4.167 , p = .042). Post-hoc Tukey HSD tests showed that only the difference between non-migrating birds and long distance migrators was significant. Approximately 40% of the variability in birds’ relative brain size is related to their pattern of migration or year-round residency. The evidence suggests that your backyard birds really may be smarter than the globe trotters who flit through from time to time.

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Spss For Oneway Anova

by E Bogue on Apr 04, 2008

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