Harman’s Single Factor Test for Common Method Bias
Harman’s single factor test checks whether one general factor explains most of the variance in your survey items, a sign of common method bias. All items enter an unrotated one-factor solution; less than 50% explained variance is the usual threshold.
Updated · By Bibin XavierData 180 × 12
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Variables and options
Results
180 rows · example dataHarman’s single factor test
| Extraction | Eigenvalue / SS loadings | % of variance | Threshold |
|---|---|---|---|
| Principal components (unrotated) | 4.976 | 45.24% | < 50% |
| Principal axis factoring (one factor) | 4.380 | 39.82% | < 50% |
Note. Podsakoff et al. (2003): if one factor accounts for the majority of covariance, common method variance may be a problem. The test is necessary but not sufficient; consider a marker variable or a common latent factor as well.
Single-factor CFA (all items on one factor)
| χ² | df | CFI | TLI | RMSEA | SRMR |
|---|---|---|---|---|---|
| 276.50 | 44 | .727 | .659 | .171 | .105 |
Note. Poor fit of a single-factor model is further evidence against a dominant method factor.
Scree plot of all items
Interpretation
A single unrotated factor explains 45.2% of the variance, below the 50% threshold, so common method bias is unlikely to be a serious concern. A single-factor CFA fits poorly (CFI = .727).
How to cite this tool
Using these results in a thesis, journal article, report or class assignment? Please cite this free tool so others can find it. It keeps the site free.
APA 7
Xavier, B. (2026). Harman’s Single Factor Test for Common Method Bias [Web application]. FreeStatisticalTools.com. https://freestatisticaltools.com/harmans-single-factor-test/
BibTeX
@software{xavier_harmanssinglefactortest_2026,
author = {Xavier, Bibin},
title = {Harman’s Single Factor Test for Common Method Bias},
publisher = {FreeStatisticalTools.com},
year = {2026},
url = {https://freestatisticaltools.com/harmans-single-factor-test/},
note = {Web application}
}Suggested sentence for your methods section: “The analysis was carried out with the free Harman’s Single Factor Test for Common Method Bias tool on FreeStatisticalTools.com (Xavier, 2026).”
What is Harman’s single factor test?
Common method bias arises when predictors and outcomes are measured with the same instrument at the same time. Harman’s single factor test loads every item on one unrotated factor; if that factor explains the majority of the variance, common method variance may be inflating the results.
When to use Harman’s single factor test
Report it in survey studies where predictors and outcomes come from the same respondents at the same time, as many journals require.
Assumptions
- All substantive items are included in one analysis.
How to use this tool
- Enter your data. Paste columns from Excel, Google Sheets or SPSS with variable names in the first row, or upload a CSV or Excel file. The example data shows the expected layout.
- Choose the variables. Select the all measurement items.
- Read the results. Results update automatically. Read the plain-English interpretation, then use Copy table to paste APA-style tables into Word and Copy for the results sentence.
How to report Harman’s single factor test in APA style
“Harman’s single factor test showed that one factor explained 31.4% of the variance, below the 50% threshold.”
Frequently asked questions
What is the threshold for Harman’s test?
If a single factor explains less than 50% of the total variance, common method bias is usually considered not to be a serious problem (Podsakoff et al., 2003).
Should I use PCA or factor analysis for Harman’s test?
Most studies report an unrotated principal component solution in SPSS; this tool shows both PCA and principal axis factoring.
Is Harman’s test enough?
It is a weak test. Reviewers increasingly expect a marker variable, a common latent factor, or full collinearity VIFs as well.
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