Психологияда зерттеу әдістері мен статистикалық талдаулар

research design and methodology in psychology

Psychological statistics is application of formulas, theorems, numbers and laws to psychology. Statistical methods for psychology include development and application statistical theory and methods for modeling psychological data. These methods include psychometrics, factor analysis, experimental designs, and Bayesian statistics. The article also discusses journals in the same field.

Psychometrics deals with measurement of psychological attributes. It involves developing and applying statistical models for mental measurements.

The reliability is computed in specific ways. (A) Inter Rater reliability: Inter Rater reliability is estimate of agreement between independent raters. This is most useful for subjective responses. Cohen's Kappa, Krippendorff's Alpha, Intra Class correlation coefficients, Correlation coefficients, Kendal's concordance coefficient, etc. are useful statistical tools. (B) Test Retest Reliability: Test Retest Procedure is estimation of temporal consistency of the test. A test is administered twice to the same sample with a time interval. Correlation between two sets of scores is used as an estimate of reliability. Testing conditions are assumed to be identical. (C) Internal Consistency Reliability: Internal consistency reliability estimates consistency of items with each other. Split half reliability (Spearman Brown Prophecy) and Cronbach Alpha are popular estimates of this reliability. (D) Parallel Form Reliability: It is an estimate of consistency between two different instruments of measurement. The inter correlation between two parallel forms of a test or scale is used as an estimate of parallel form reliability.

Validity of a scale or test is ability of the instrument to measure what it purports to measure.

The modern test theory is based on latent trait model. Every item estimates the ability of the test taker. The ability parameter is called as theta (θ). The difficulty parameter is called b. the two important assumptions are local independence and unidimensionality. The Item Response Theory has three models. They are one parameter logistic model, two parameter logistic model and three parameter logistic model. In addition, Polychromous IRT Model are also useful. The R Software has ‘ltm’, packages useful for IRT analysis.

Factor analysis is at the core of psychological statistics. It has two schools: (1) Exploratory Factor analysis (2) Confirmatory Factor analysis.

The exploratory factor analysis begins without a theory or with a very tentative theory. It is a dimension reduction technique. It is useful in psychometrics, multivariate analysis of data and data analytics. Typically a k dimensional correlation matrix or covariance matrix of variables is reduced to k X r factor pattern matrix where r < k. Principal Component analysis and common factor analysis are two ways of extracting data. Principal axis factoring, ML factor analysis, alpha factor analysis and image factor analysis is most useful ways of EFA. It employs various factor rotation methods which can be classified into orthogonal (resulting in uncorrelated factors) and oblique (resulting correlated factors). The ‘psych’ package in R is useful for EFA.

Experimental methods are very popular in psychology, going back more than 100 years. Experimental psychology is a sub discipline of psychology Statistical methods applied for designing and analyzing experimental psychological data include the t test, ANOVA, ANCOVA, MANOVA, MANCOVA, binomial test, chi square, etc.

Multivariate behavioral research is becoming very popular in psychology. These methods include Multiple Regression and Prediction; Moderated and Mediated Regression Analysis; Logistics Regression; Canonical Correlations; Cluster analysis; Multi level modeling; Survival Failure analysis; Structural Equations Modeling; hierarchical linear modelling, etc. are very useful for psychological statistics.

Various software packages are available for statistical methods for psychological research. They can be classified as commercial software (e. g., JMP and SPSS) and open source (e. g., R). Among the open source offerings, the R software is the most popular. There are many online references for R and specialized books on R for Psychologists are also being written. The "psych" package of R is very useful for psychologists. Among others, "lavaan", "sem", "ltm", "ggplot2" are some of the popular packages. PSPP and KNIME are other free packages. Commercial packages include JMP, SPSS and SAS. JMP and SPSS are commonly reported in books.