Basic Psychology: Quantitative psychology

Introduction
History
Education and training
Research areas
Professional organizations

Introduction

Quantitative psychology is a branch of psychology that studies mathematical modelling, research design and methodology, and statistical analysis of psychological processes. It consists of tests and other devices for assessing cognitive abilities. Quantitative psychologists create and analyse a wide range of research methods, including those of psychometrics, a branch of psychology concerned with the theory and practise of psychological measurement.

Psychologists have long contributed to statistical and mathematical analysis, and the American Psychological Association now recognises quantitative psychology as a specialty. A number of universities in Europe and North America award doctoral degrees in this field, and quantitative psychologists are in high demand in industry, government, and academia. Their education in both social science and quantitative methodology provides them with a unique skill set for solving applied and theoretical problems in a variety of fields.

History

Quantitative psychology has its roots in early experimental psychology, when the scientific method was first systematically applied to psychological phenomena in the nineteenth century. E. H. Weber's studies of tactile sensitivity (1930s), Fechner's development and use of psychophysical methods (1850-1860), and Helmholtz's research on vision and audition beginning after 1850 were all significant contributions. Wilhelm Wundt is often referred to as the "Father of Experimental Psychology," because he identified as a psychologist and established a psychological laboratory in 1879, where many researchers came to study. The work of these and many others helped to disprove theorists like Immanuel Kant's claim that psychology could never become a science because precise experiments on the human mind were impossible.

Intelligence testing

For many years, intelligence testing has been a vital part of quantitative psychology. Francis Galton, a pioneer in psychometrics in the nineteenth century, was the first to develop a standardised test of intelligence and one of the first to apply statistical methods to the study of human differences and their inheritance. He came to believe that intelligence is largely determined by heredity, and he also hypothesised that other measures of intelligence, such as reflex speed, muscle strength, and head size, are related to intelligence. In 1882, he founded the world's first mental testing centre, and the following year, he published his findings and theories in "Inquiries into Human Faculty and Its Development."

Statistical techniques

Statistical methods are the most commonly used quantitative tools by psychologists. Pearson developed the correlation coefficient as well as the chi-squared test. During the period 1900–1920, the t-test (Student, 1908), the ANOVA (Fisher, 1925), and a nonparametric correlation coefficient were developed (Spearman, 1904). In the latter half of the twentieth century, a large number of tests were developed (e.g., all the multivariate tests). Popular techniques (such as Arnold's (1992) Hierarchical Linear Model, Byrne's (1996) Structural Equation Modeling, and Hyvarinn, Karhunen, and Oja's (2001) Independent Component Analysis) are relatively new.

In a paper that is still frequently cited, psychologist Stanley Smith Stevens organised levels of measurement into four scales, Nominal, Ordinal, Ratio, and Interval, in 1946. Jacob Cohen, a psychology professor at New York University, studied quantitative methods involving statistical power and effect size, which helped to lay the groundwork for current statistical meta-analysis and statistical estimation methods. Cohen's name was given to him by him.

In 1990, the American Psychologist journal published an influential paper titled "Graduate Training in Statistics, Methodology, and Measurement in Psychology." This article discussed the need for increased and up-to-date quantitative methods training in US psychology graduate programmes.

Education and training

Undergraduate

Training in quantitative psychology can begin Informally at the undergraduate level. Many graduate schools recommend that students take some psychology courses as well as the full college sequence of calculus (including multivariate calculus) and linear algebra. Quantitative courses in other fields, such as economics and research methods and statistics for psychology majors, are also beneficial. Students without all of these courses have been accepted in the past if other aspects of their application show promise. Some schools also provide formal minors in quantitative psychology. The University of Kansas, for example, offers a minor in "Social and Behavioral Sciences Methodology," which offers advanced training in research methodology, applied data analysis, and practical research experience relevant to quantitative psychology. Computer science coursework is also beneficial. Mastering an object-oriented programming language or learning to write code in SPSS or R is beneficial for the type of data analysis done in graduate school.

Graduate

Quantitative psychologists can hold either a doctorate or a master's degree. Because of their interdisciplinary nature, and depending on the university's research focus, these programmes may be housed in a school's college of education or in their psychology department. Educational research and psychometrics programmes are frequently part of education or educational psychology departments. As a result, these programmes may have different names that include the words "research methods" or "quantitative methods," such as the Ph.D. in "Research and Evaluation Methodology" from the University of Florida or the "Quantitative Methods" degree from the University of Pennsylvania. Some universities, however, may have separate programmes in their two colleges. The University of Washington, for example, offers a "Quantitative Psychology" degree in the psychology department as well as a separate "Measurement & Statistics" Ph.D. in the college of education. Others, like Vanderbilt University's Ph.D. in Psychological Sciences, are shared by the university's two psychology departments.

McGill University's "Quantitative Psychology and Modeling" programme and Purdue University's "Mathematical and Computational Cognitive Science" degrees are two examples of universities with a mathematical focus. Students who are interested in modelling biological or functional data may pursue careers in biostatistics or computational neuroscience.

Doctoral programmes typically accept students with only bachelor's degrees, though some schools may require a master's degree prior to admission. Graduate students typically earn a Master of Arts in Psychology, a Master of Science in Statistics or Applied Statistics, or both after the first two years of study.

In addition, several universities, including New York University, offer minor concentrations in quantitative methods.

Some of the largest private sector employers of quantitative psychologists are companies that create standardised tests, such as College Board, Educational Testing Service, and American College Testing. These companies also frequently offer internships to graduate students.

Shortage of qualified applicants

The American Psychological Association expressed a need for more quantitative psychologists in the industry in August 2005, stating that for every PhD awarded in the subject, there were approximately 2.5 quantitative psychologist job openings. Due to a lack of qualified applicants in the field, the APA formed a Task Force to investigate the current state of quantitative psychology and forecast its future. Domestic applicants from the United States are especially scarce. The vast majority of international applicants are from Asia, particularly South Korea and China. In 2006, the APA Council of Representatives established a special task force in response to a lack of qualified applicants. Leona S. Aiken of Arizona State University presided over the task force.

Research areas

Quantitative psychologists typically specialise in one area of study. Item response theory and computer adaptive testing, which focus on education and intelligence testing, are notable research areas in psychometrics. Other research areas include time series analysis for modelling psychological processes, such as in fMRI data collection, structural equation modelling, social network analysis, human decision science, and statistical genetics.

A common type of psychometric test is an aptitude test, which is designed to assess raw intellectual suitability for a specific purpose, and a personality test, which is designed to assess character, temperament, and problem-solving abilities.

The application of related mathematical models to testing data is the foundation of item response theory. It is the preferred method for developing scales in the United States because it is widely regarded as superior to classical test theory, particularly when optimal decisions are required, as in so-called high-stakes tests such as the Graduate Record Examination (GRE) and Graduate Management Admission Test (GMAT).

Professional organizations

Several scientific organisations support quantitative psychology. The Psychometric Society, the American Psychological Association's Division 5 (Evaluation, Measurement, and Statistics), the Society of Multivariate Experimental Psychology, and the European Society for Methodology are among them. Statistics, mathematics, educational measurement, educational statistics, sociology, and political science are all related fields. Several scholarly journals, including Psychometrika, Multivariate Behavioral Research, Structural Equation Modeling, and Psychological Methods, reflect the efforts of scientists in these areas.