Factor analysis reduces and analyses large sets of data to identify underlying factors, and assess their influence on a set of measured variables. Survey researchers commonly use factor analysis to determine what unmeasured factors influence responses to a set of survey questions. This complex procedure requires use of a specialised statistical software program, such as SPSS. An IBM-owned company, SPSS leads the user through a series of simple steps needed to complete the two stages of factor analysis: factor extraction and factor rotation.

- Skill level:
- Moderate

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### Things you need

- Computer, with SPSS software installed
- Data

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## Instructions

- 1
Open the SPSS data file you wish to analyse. Then, click "Analyze" in the menu bar at the top of the SPSS spreadsheet. This opens a pull-down menu with a series of data analysis tools and procedures. Select the option labelled "Data Reduction" or "Dimension Reduction," depending on which version of SPSS you have. Then select "Factor Analysis," which opens a factor analysis dialogue box.

- 2
Select the variables you want to include in your factor analysis by choosing the variable name and clicking an arrow key, which moves the variable into a box labelled "Variables."

- 3
Click "Extraction" in the factor analysis dialogue box in SPSS. This will open an extraction dialogue box, which will indicate that SPSS will run a principal components factor analysis, extracting eigenvalues greater than one and displaying an unrotated factor solution. Click "Continue," which returns you to the factor analysis dialogue box.

- 4
Click "OK" in the factor analysis dialogue box. SPSS will run the factor extraction procedure, displaying the results in an output file. You can view your results there before proceeding to the factor rotation stage.

- 1
Click "Analyze," then select "Data Reduction" or "Dimension Reduction," followed by "Factor Analysis." This will open the factor analysis dialogue box, which should display the variables you analysed in the factor extraction stage.

- 2
Click "Extraction," and in the extraction dialogue box, under Extract, select the "Number of Factors" option and then type the number of factors to rotate. In factor analysis, the general guideline is to choose the number of factors equal to the number of eigenvalues with values greater than one. Check the factor extraction results in your SPSS output file to see how many eigenvalues exceed one. After choosing the number of factors, click "Continue" to return to the factor analysis dialogue box.

- 3
Click "Rotation," which opens a factor rotation dialogue box. In this box, choose the type of rotation method you want. In most cases, choosing Varimax is the preferred option. This procedure will analyse the variables, counting the correlations that exist among the variables and underlying factors.

- 4
View and interpret the results of your analysis in the SPSS output file.