Derivation of theory by means of factor analysis or Tom Swift and his electric factor analysis machine
Open accessAbstract
Problems in the use of factor analysis for deriving theory are illustrated by means of an example in which the underlying factors are known. The actual underlying model is simple and it provides a perfect explanation of the data. While the factor analysis 'explains' a large proportion of the total variance, it fails to identify the known factors in the model, The illustration is used to emphasize that factor analysis, by itself, may be misleading as far as the development of theory is concerned. The use of a comprehensive, and explicit à priori analysis is proposed so that there will be independent criteria for the evaluation of the factor analytic results.
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Cites
The dimensions of culture patterns by factorization of national characters.
Cattell, R. B. (1949) · Journal of Abnormal & Social Psychology · doi:10.1037/h0054760 · Cited by 105 · see citing works
Note on the scientific status of factors.
Overall, J. E. (1964) · Psychological Bulletin · doi:10.1037/h0046664 · Cited by 36 · see citing works
Flagged first, then by citations
Cited by
Sorted by citations
Evaluating the use of exploratory factor analysis in psychological research.
Fabrigar, L. R., Wegener, D. T., MacCallum, R. C., & Strahan, E. J. (1999) · Psychological Methods · doi:10.1037/1082-989x.4.3.272 · Cited by 9,587 · see citing works
Exploratory and confirmatory factor analysis: Understanding concepts and applications.
Thompson, B. (2004) · doi:10.1037/10694-000 · Cited by 3,469 · see citing works
Text as Data: The Promise and Pitfalls of Automatic Content Analysis Methods for Political Texts
Grimmer, J., & Stewart, B. M. (2013) · Political Analysis · doi:10.1093/pan/mps028 · Cited by 3,297 · see citing works
THE APPLICATION OF EXPLORATORY FACTOR ANALYSIS IN APPLIED PSYCHOLOGY: A CRITICAL REVIEW AND ANALYSIS
Ford, J. K., MacCallum, R. C., & Tait, M. (1986) · Personnel Psychology · doi:10.1111/j.1744-6570.1986.tb00583.x · Cited by 1,735 · see citing works
A contrarian view of the five-factor approach to personality description.
Block, J. (1995) · Psychological Bulletin · doi:10.1037/0033-2909.117.2.187 · Cited by 1,682 · see citing works
Antonakis, J., Avolio, B. J., & Sivasubramaniam, N. (2003) · The Leadership Quarterly · doi:10.1016/s1048-9843(03)00030-4 · Cited by 1,533 · see citing works
The contingency theory of management accounting: Achievement and prognosis
Otley, D. T. (1980) · Accounting Organizations and Society · doi:10.1016/0361-3682(80)90040-9 · Cited by 1,134 · see citing works
The contingency theory of management accounting: achievement and prognosis
Otley, D. T. (1980) · Springer eBooks · doi:10.1007/978-1-4899-7138-8_5 · Cited by 1,116 · see citing works
Multivariate Analysis in Ecology and Systematics: Panacea or Pandora's Box?
James, F. C., & McCulloch, C. E. (1990) · Annual Review of Ecology and Systematics · doi:10.1146/annurev.es.21.110190.001021 · Cited by 1,032 · see citing works
Structural analysis of social behavior.
Benjamin, L. S. (1974) · Psychological Review · doi:10.1037/h0037024 · Cited by 1,011 · see citing works
Thompson, B., & Daniel, L. G. (1996) · Educational and Psychological Measurement · doi:10.1177/0013164496056002001 · Cited by 919 · see citing works
Repairing Tom Swift's Electric Factor Analysis Machine
Preacher, K. J., & MacCallum, R. C. (2003) · Understanding Statistics · doi:10.1207/s15328031us0201_02 · Cited by 860 · see citing works
Emotional labor: A conceptualization and scale development
Glomb, T. M., & Tews, M. J. (2003) · Journal of Vocational Behavior · doi:10.1016/s0001-8791(03)00038-1 · Cited by 541 · see citing works
Psychographics: A Critical Review
Wells, W. D. (1975) · Journal of Marketing Research · doi:10.1177/002224377501200210 · Cited by 529 · see citing works
A JUDGEMENTAL INTERNATIONAL CLASSIFICATION OF FINANCIAL REPORTING PRACTICES
Nobes, C. W. (1983) · Journal of Business Finance & Accounting · doi:10.1111/j.1468-5957.1983.tb00409.x · Cited by 354 · see citing works
Patil, V. H., Singh, S. N., Mishra, S. K., & Donavan, D. T. (2007) · Journal of Business Research · doi:10.1016/j.jbusres.2007.05.008 · Cited by 326 · see citing works
Receptor modeling application framework for particle source apportionment
Watson, J. G., Zhu, T., Chow, J. C., Engelbrecht, J. P., Fujita, E. M., & Wilson, W. E. (2002) · Chemosphere · doi:10.1016/s0045-6535(02)00243-6 · Cited by 299 · see citing works
Statistical issues with microarrays: processing and analysis
Nadon, R., & Shoemaker, J. S. (2002) · Trends in Genetics · doi:10.1016/s0168-9525(02)02665-3 · Cited by 297 · see citing works
A Renaissance of Political Culture?
Jackman, R. W., & Miller, R. A. (1996) · American Journal of Political Science · doi:10.2307/2111787 · Cited by 284 · see citing works
Rogers, R. G., Rockwood, T. H., Constantine, M. L., Thakar, R., KAMMERER-DOAK, D. N., Pauls, R. N., Parekh, M. H., Ridgeway, B., Jha, S., Pitkin, J., et al. (2013) · International Urogynecology Journal · doi:10.1007/s00192-012-2020-8 · Cited by 204 · see citing works
General geomorphometry, derivatives of altitude, and descriptive statistics
Evans, I. S. (2019) · Routledge eBooks · doi:10.4324/9780429273346-2 · Cited by 200 · see citing works
Dimensions of State Politics, Economics, and Public Policy
Sharkansky, I., & Hofferbert, R. I. (1969) · American Political Science Review · doi:10.1017/s0003055400258632 · Cited by 198 · see citing works
General purpose computer-assisted clustering and conceptualization
Grimmer, J., & King, G. (2011) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.1018067108 · Cited by 179 · see citing works
Events That Increase Uncertainty in Personal Relationships II Replication and Extension
Planalp, S., RUTHERFORD, D. K., & Honeycutt, J. M. (1988) · Human Communication Research · doi:10.1111/j.1468-2958.1988.tb00166.x · Cited by 149 · see citing works
THE ROLE OF CONFIRMATORY FACTOR ANALYSIS IN CROSS‐CULTURAL RESEARCH*
Watkins, D. (1989) · International Journal of Psychology · doi:10.1080/00207598908247839 · Cited by 144 · see citing works
DISTINGUISHING FACTS AND ARTIFACTS IN GROUP‐BASED MODELING*
Skarðhamar, T. (2010) · Criminology · doi:10.1111/j.1745-9125.2010.00185.x · Cited by 141 · see citing works
Phobic dimensions: IV. The structure of animal fears
Arrindell, W. A. (2000) · Behaviour Research and Therapy · doi:10.1016/s0005-7967(99)00097-2 · Cited by 135 · see citing works
Marketing measurement revolution
Rossiter, J. R. (2011) · European Journal of Marketing · doi:10.1108/03090561111167298 · Cited by 133 · see citing works
The Data Puzzle: The Nature of Interpretation in Quantitative Research
Kritzer, H. M. (1996) · American Journal of Political Science · doi:10.2307/2111692 · Cited by 107 · see citing works
Possible Limits on a Science of Social Behavior
Thorngate, W. (1976) · Springer eBooks · doi:10.1007/978-1-4615-8765-1_9 · Cited by 104 · see citing works
Rivers as Sentinels: Using the Biology of Rivers to Guide Landscape Management
Karr, J. R. (1998) · Springer eBooks · doi:10.1007/978-1-4612-1652-0_20 · Cited by 99 · see citing works
Anderson, R. D., Engledow, J. L., & Becker, H. (1979) · Journal of Marketing Research · doi:10.1177/002224377901600312 · Cited by 96 · see citing works
Das Anorexia-nervosa-Inventar zur Selbstbeurteilung (ANIS)
Fichter, M. M., & Keeser, W. (1980) · European Archives of Psychiatry and Clinical Neuroscience · doi:10.1007/bf00365746 · Cited by 90 · see citing works
Deaton, A. (1986) · Handbook of econometrics · doi:10.1016/s1573-4412(86)03010-6 · Cited by 83 · see citing works
Using college students' self‐reported learning outcomes in scholarly research
Pike, G. (2011) · New Directions for Institutional Research · doi:10.1002/ir.388 · Cited by 80 · see citing works
Questionable Multivariate Statistical Inference in Wildlife Habitat and Community Studies
Rexstad, E. A., Miller, D. D., Flather, C. H., Anderson, E. M., Hupp, J. W., & Anderson, D. R. (1988) · Journal of Wildlife Management · doi:10.2307/3800948 · Cited by 81 · see citing works
Factor analysis in geochemical exploration
Tripathi, V. S. (1979) · Journal of Geochemical Exploration · doi:10.1016/0375-6742(79)90004-9 · Cited by 80 · see citing works
A Progressive Supervised-learning Approach to Generating Rich Civil Strife Data
Nardulli, P. F., Althaus, S. L., & Hayes, M. (2015) · Sociological Methodology · doi:10.1177/0081175015581378 · Cited by 78 · see citing works
Microhabitat Analysis Using Radiotelemetry Locations and Polytomous Logistic Regression
North, M. P., & Reynolds, J. H. (1996) · Journal of Wildlife Management · doi:10.2307/3802083 · Cited by 78 · see citing works
Exploratory and Confirmatory Factor Analysis: Understanding Concepts and Applications
Zientek, L. R. (2008) · Structural Equation Modeling A Multidisciplinary Journal · doi:10.1080/10705510802339122 · Cited by 75 · see citing works
Cultural Values, Stable Democracy, and Economic Development: A Reply
Granato, J., Inglehart, R., & Leblang, D. A. (1996) · American Journal of Political Science · doi:10.2307/2111789 · Cited by 71 · see citing works
On the Use and Limitations of Trend Surface Models
Norcliffe, G. B. (1969) · Canadian Geographies / Géographies canadiennes · doi:10.1111/j.1541-0064.1969.tb01197.x · Cited by 70 · see citing works
Zelditch, M. L. (1987) · Systematic Zoology · doi:10.2307/2413401 · Cited by 69 · see citing works
Topics, Concepts, and Measurement: A Crowdsourced Procedure for Validating Topics as Measures
Ying, L., Montgomery, J., & Stewart, B. (2021) · Political Analysis · doi:10.1017/pan.2021.33 · Cited by 64 · see citing works
Stanimirova, I., Tauler, R., & Walczak, B. (2011) · Environmental Science & Technology · doi:10.1021/es201024m · Cited by 62 · see citing works
Data mining: data analysis on a grand scale?
Smyth, P. (2000) · Statistical Methods in Medical Research · doi:10.1177/096228020000900402 · Cited by 60 · see citing works
The Role of Hypothesis Testing in Wildlife Science
Johnson, D. H. (2002) · Journal of Wildlife Management · doi:10.2307/3803159 · Cited by 60 · see citing works
Ferguson, G., Megehee, C. M., & Woodside, A. G. (2017) · Tourism Management · doi:10.1016/j.tourman.2017.05.001 · Cited by 59 · see citing works
An investigation of dimensions of cognitive appraisal in emotion using the repertory grid technique
Reisenzein, R., & Hofmann, T. (1990) · Motivation and Emotion · doi:10.1007/bf00995546 · Cited by 58 · see citing works
Chen, C., Fang, X., Xiang, W., Lei, P., Ouyang, S., & Kuzyakov, Y. V. (2020) · Forest Ecosystems · doi:10.1186/s40663-020-00242-3 · Cited by 57 · see citing works
Nonmetric Multidimensional Scaling: A Monte Carlo Study of the Basic Parameters
Sherman, C. R. (1972) · Psychometrika · doi:10.1007/bf02306786 · Cited by 57 · see citing works
Ashkanasy, N. M. (1985) · Journal of Personality and Social Psychology · doi:10.1037/0022-3514.48.5.1328 · Cited by 55 · see citing works
M-AMBI revisited: looking inside a widely-used benthic index
Sigovini, M., Keppel, E., & Tagliapietra, D. (2013) · Hydrobiologia · doi:10.1007/s10750-013-1565-y · Cited by 53 · see citing works
Commentary on quantitative methods in I-O research
MacCallum, R. C. (1998) · PsycEXTRA Dataset · doi:10.1037/e577062011-002 · Cited by 52 · see citing works
On the Dimensions of Political Alienation in America
Mason, W. M., House, J. S., & Martin, S. S. (1985) · Sociological Methodology · doi:10.2307/270848 · Cited by 51 · see citing works
Trofimova, I. N., Robbins, T. W., Sulis, W., & Uher, J. (2018) · Philosophical Transactions of the Royal Society B Biological Sciences · doi:10.1098/rstb.2017.0152 · Cited by 50 · see citing works
Postmaterialism in World Societies: Is It Really a Value Dimension?
Davis, D. W., Dowley, K. M., & Silver, B. D. (1999) · American Journal of Political Science · doi:10.2307/2991841 · Cited by 49 · see citing works
A Comparison of Factor Analysis Programs in SPSS, BMDP, and SAS
MacCallum, R. C. (1983) · Psychometrika · doi:10.1007/bf02294017 · Cited by 49 · see citing works
Greene, A. L., Watts, A. L., Forbes, M. K., Kotov, R., Krueger, R. F., & Eaton, N. R. (2022) · Psychological Methods · doi:10.1037/met0000465 · Cited by 46 · see citing works
A Simulation Study of Factor Score Indeterminacy
Acito, F., & Anderson, R. D. (1986) · Journal of Marketing Research · doi:10.1177/002224378602300203 · Cited by 46 · see citing works
An inductive typology of egocentric networks
Giannella, E., & Fischer, C. S. (2016) · Social Networks · doi:10.1016/j.socnet.2016.02.003 · Cited by 45 · see citing works
The "stuff" of hypnotic performance: A review of psychometric approaches.
Balthazard, C. G., & Woody, E. Z. (1985) · Psychological Bulletin · doi:10.1037/0033-2909.98.2.283 · Cited by 42 · see citing works
Thoughts on the Analysis of Group-Based Developmental Trajectories in Criminology
Brame, R. W., Paternoster, R., & Piquero, A. R. (2011) · Justice Quarterly · doi:10.1080/07418825.2011.585994 · Cited by 38 · see citing works
Agyeman, S., & Cheng, L. (2020) · Transport Policy · doi:10.1016/j.tranpol.2020.08.015 · Cited by 35 · see citing works
The Role of Confirmatory Factor Analysis in Cross-Cultltral Research
Watkins, D. (1989) · International Journal of Psychology · doi:10.1080/00207598908246806 · Cited by 34 · see citing works
Blind Analysis as a Correction for Confirmatory Bias in Physics and in Psychology
MacCoun, R. J., & Perlmutter, S. (2017) · doi:10.1002/9781119095910.ch15 · Cited by 30 · see citing works
Diversion and Political Survival in Latin America
Miller, R. A., & Elgün, Ö. (2010) · Journal of Conflict Resolution · doi:10.1177/0022002710381064 · Cited by 28 · see citing works
Crowson, C. S., Gunderson, T. M., Davis, J. M., Myasoedova, E., Kronzer, V. L., Coffey, C. M., & Atkinson, E. J. (2022) · Arthritis Care & Research · doi:10.1002/acr.24973 · Cited by 27 · see citing works
Measuring the ‘balances of power’: a look at some numbers
Moul, W. B. (1989) · Review of International Studies · doi:10.1017/s0260210500112951 · Cited by 27 · see citing works
Association of Self-Rated Physical Health and Incident Hypertension With O*NET Factors
Meyer, J. D., Cifuentes, M., & Warren, N. (2011) · Journal of Occupational and Environmental Medicine · doi:10.1097/jom.0b013e318203f220 · Cited by 25 · see citing works
Gardiner, V. (1978) · Transactions of the Institute of British Geographers · doi:10.2307/622121 · Cited by 23 · see citing works
Peer evaluation: its potential usefulness in medical education
Helfer, R. E. (1972) · Medical Education · doi:10.1111/j.1365-2923.1972.tb01662.x · Cited by 23 · see citing works
Factorial Ecology and Factor Invariance: An Investigation
Giggs, J. A., & Mather, P. M. (1975) · Economic Geography · doi:10.2307/142921 · Cited by 21 · see citing works
Eigenvalue Shrinkage in Principal Components Based Factor Analysis
Bobko, P., & Schemmer, F. M. (1984) · Applied Psychological Measurement · doi:10.1177/014662168400800408 · Cited by 20 · see citing works
Horizontal distribution of planktonic diatoms in Green Bay, mid‐July 19701
Holland, R. E., & Claflin, L. W. (1975) · Limnology and Oceanography · doi:10.4319/lo.1975.20.3.0365 · Cited by 20 · see citing works
Caratti, J. F., Nesser, J. A., & Maynard, C. L. (2004) · JAWRA Journal of the American Water Resources Association · doi:10.1111/j.1752-1688.2004.tb01584.x · Cited by 19 · see citing works
A Validation Study of an Instrument Designed to Measure Teaching Effectiveness
Pike, C. K. (1998) · Journal of Social Work Education · doi:10.1080/10437797.1998.10778922 · Cited by 19 · see citing works
Wilding, M., Chae, K., & Jang, J. (2014) · Public Performance & Management Review · doi:10.1080/15309576.2015.983838 · Cited by 18 · see citing works
A Study of the Role of Beliefs and Intentions in Consistency Restoration
Olshavsky, R. W., & Summers, J. O. (1974) · Journal of Consumer Research · doi:10.1086/208582 · Cited by 17 · see citing works
Yuen, E. Y. N., Knight, T., Dodson, S., Chirgwin, J. H., Busija, L., Ricciardelli, L. A., Burney, S., Parente, P., & Livingston, P. M. (2017) · Health & Social Care in the Community · doi:10.1111/hsc.12524 · Cited by 16 · see citing works
Scherer, A., Eberle, N., Boecker, M., Vögele, C., Gauggel, S., & Forkmann, T. (2013) · BMC Psychiatry · doi:10.1186/1471-244x-13-16 · Cited by 16 · see citing works
Developing an identity fraud measurement model: a factor analysis approach
Lavassani, K. M., Kumar, V., Movahedi, B. M., & Kumar, U. (2009) · Journal of Financial Crime · doi:10.1108/13590790910993708 · Cited by 15 · see citing works
Koniewski, M. (2018) · European Journal of Psychological Assessment · doi:10.1027/1015-5759/a000475 · Cited by 17 · see citing works
Grimmer, J., & King, G. (2009) · Cited by 14 · see citing works
Data Mining at the Interface of Computer Science and Statistics
Smyth, P. (2001) · Massive computing · doi:10.1007/978-1-4615-1733-7_3 · Cited by 14 · see citing works
A Simulation Study of Methods for Hypothesis Testing in Factor Analysis
Acito, F., Anderson, R. D., & Engledow, J. L. (1980) · Journal of Consumer Research · doi:10.1086/208803 · Cited by 14 · see citing works
Spatial scale and drainage basin morphometric interaction
Ebisemiju, F. S. (1985) · CATENA · doi:10.1016/0341-8162(85)90017-7 · Cited by 14 · see citing works
Conroy, M. J., Stodola, K. W., & Cooper, R. J. (2011) · Journal für Ornithologie · doi:10.1007/s10336-011-0687-0 · Cited by 13 · see citing works
Conway, D., & Haynes, K. E. (1977) · Environment and Planning A Economy and Space · doi:10.1068/a091143 · Cited by 13 · see citing works
The Borderline of Science: On the Value of Factor Analysis for Understanding Presence
Waller, D. A., & Bachmann, E. R. (2006) · PRESENCE Virtual and Augmented Reality · doi:10.1162/pres.2006.15.2.235 · Cited by 12 · see citing works
Conformity and Deviance in the "Situation of Company"
Empey, L. T., & Lubeck, S. G. (1968) · American Sociological Review · doi:10.2307/2092886 · Cited by 12 · see citing works
Watkins, D., & Hattie, J. (1981) · Australian Journal of Psychology · doi:10.1080/00049538108254697 · Cited by 12 · see citing works
The development and psychometric properties of a self-report Catastrophizing Questionnaire
Pike, A. C., Serfaty, J., & Robinson, O. J. (2021) · Royal Society Open Science · doi:10.1098/rsos.201362 · Cited by 11 · see citing works
Realism and Uncertainty of Unobservable Common Causes in Factor Analysis
Johnson, K. R. (2014) · Noûs · doi:10.1111/nous.12075 · Cited by 11 · see citing works
Factor-Analytic Evidence for the Complexity of the Delis–Kaplan Executive Function System (D-KEFS)
McFarland, D. J. (2019) · Assessment · doi:10.1177/1073191119843584 · Cited by 11 · see citing works
An Empirical Comparison of Two Methods for Testing the Significance of a Correlation Matrix
Wilson, G. A., & Martin, S. A. (1983) · Educational and Psychological Measurement · doi:10.1177/001316448304300102 · Cited by 11 · see citing works
Mirror, Mirror. . . .: Down with the Linear Model
Brown, D. J. (1975) · American Educational Research Journal · doi:10.3102/00028312012004491 · Cited by 11 · see citing works
Larson, J. H., Busby, D. M., Wilson, S. M., Medora, N. P., & Allgood, S. M. (1994) · Journal of Counseling & Development · doi:10.1002/j.1556-6676.1994.tb00942.x · Cited by 11 · see citing works
External and Internal Conflict Behavior Among Nations, 1966-1967
Eberwein, W., Hübner-Dick, G., Jagodzinski, W., Rattinger, H., & Weede, E. (1979) · Journal of Conflict Resolution · doi:10.1177/002200277902300407 · Cited by 11 · see citing works
Maldonado, J. S., Coria, M. D. C. D., Orellana, L., Criado, N., Mendoza, J., Salazar, P., & Yung, G. (2017) · Interdisciplinaria Revista de Psicología y Ciencias Afines · doi:10.16888/interd.2017.34.1.7 · Cited by 10 · see citing works
- Authors
- Armstrong, J. S.
- Affiliations
- Massachusetts Institute of Technology (US)
- Corresponding author
- Armstrong, J. Scott
- Venue
- The American Statistician
- Publisher
- Informa UK Limited
- Published
- 1967-12
- Volume
- 21
- Issue
- 5
- Pages
- 17-21
- ISSN
- 0003-1305 (ISSN-L)
- 1537-2731
- OpenAlex
- W2107760749
- Cited by
- 165
- References
- 2
- Citations by year
- 2026: 1 · 2025: 4 · 2024: 2 · 2023: 4 · 2022: 3 · 2021: 2 · 2020: 2 · 2019: 4 · 2018: 3 · 2017: 5 · 2016: 2 · 2015: 4 · 2014: 5 · 2013: 5
- FWCI
- 2.66
- Type
- journal article
- Language
- en
- Open access
- green
- repository.upenn.edu
- Locations
- The American Statistician (publishedVersion)
- Scholarly Commons (University of Pennsylvania) (submittedVersion)
- RePEc: Research Papers in Economics (submittedVersion)
- ScholarlyCommons (University of Pennsylvania) (submittedVersion)
- General Economics and Teaching (submittedVersion)
- DSpace@MIT (Massachusetts Institute of Technology) (submittedVersion, cc-by-nc)
- Topics
- Social Sciences › Decision Sciences › Management Science and Operations Research › Psychometric Methodologies and Testing
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Applications
- Social Sciences › Education › Diverse Academic Research Areas
- Keywords
- factor analysis, theory development, a priori analysis, system identification, scientific method, Tom Swift
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