A quick review of steps for the 1-way within subjects ANOVA

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Background | Enter Data | Analyze Data | Interpret Data | Report Data

I. Enter your data into three columns in the data file

 

  1. Use the first column of the data file to enter DV data collected in your first condition.
  2. Give the first column a meaningful name. This name should help you to know that you are looking at data from the first condition.
  3. Use the second column of the data file to enter data collected from the second condition of your experiment. 
  4. Give the second column a meaningful name. This name should help you to know that you are looking at data from the second condition.
  5. Use the third column of the data file to enter DV data collected in your third condition.
  6. Give the third column a meaningful name. This name should help you to know that you are looking at data from the third condition.
  7. Save the data file to a meaningful place with a meaningful name. This file should have a .sav extension.

II. Analyze your data

 

  1. Click Analyze, General Linear Model and then Repeated Measures. A Repeated Measures Define Factor(s) box will appear.
  2. Fill in the blank for the Within-Subject Factor Name box. Use the name of the IV, the name “Factor1” or the name “level.”
  3. Fill in a number for the Number of Levels box. The number you choose will depend on how many IV conditions you have. If you have 3 IV conditions for example, enter the number 3.
  4. Click the Add button.
  5. Click the Define button. You will see a Repeated Measures box.
  6. Transfer each condition name in the window on the left to the window on the upper right. Do this by clicking on each condition name and clicking on the corresponding arrow.
  7. Click the Options button. You will see a Repeated Measures: Option box.
  8. Click on the empty box next to the words “Descriptive statistics.” Once clicked, you will see a check in this box.
  9. Click the Continue button. You will return to the Repeated Measures box.
  10. Click the OK button and wait a few seconds for processing.
  11. You will see your results. Save the results to a meaningful place with a meaningful name. SPSS should give the output file a .spo extension.

 

III. Interpret your results

 

  1. Look in the Descriptive Statistics box for condition means, standard deviations and number of participants.
  2. Make sure the number of participants for each condition is accurate. If it is not, go back to the data file and make sure it is correct.
  3. Look in the Multivariate Tests box.
  4. Check the Sig value in the row labeled “Wilks’ Lambda” to determine if there was a statistically significant difference between group means. If the Sig value is greater than .05, you can conclude that there is no statistically significant difference between your conditions – that the IV did not have a significant effect on the DV. However, if the Sig value is less than or equal to .05, you can conclude that there is a statistically significant difference between some or all of your conditions. This means that it is likely that the IV did have an effect on the DV and the results were not likely due to chance.
  5. If the Sig. value is less than or equal to .05, you will need to conduct post hoc Paired Samples T-Tests to compare each condition to every other condition. To do this, follow the instructions in the Paired Samples T-Test chapters with one difference. Rather than using the number .05 to compare with the Sig (2-Tailed) value, use the number .05 divided by the number of conditions that you have. For example, if you have three conditions, us .05/3  = 0.017 as the number to compare your Sig (2-Tailed) value to.

 

IV. Report your results

 

  1. Report the type of test used and what it was used to test.
  2. Report whether or not there was a significant difference between your conditions. Include the group means, standard deviation, and the Sig. values.
  3. If there was a significant difference between your conditions as determined by the 1-Way ANOVA, report the results of the series of post hoc Paired Samples T-Tests that you have conducted to compare each condition to every other condition. Following the instructions for reporting the results of Paired Samples T-Tests in the previous chapters on this topic with one exception. Remember to determine significance based on whether the Sig (2-Tailed) values are greater, less than or equal to .05 divided by the number of IV conditions.
  4. Report your results in words that people can understand.

Background | Enter Data | Analyze Data | Interpret Data | Report Data
 

 

 

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