NCJ Number
66666
Journal
Evaluation Review Volume: 4 Issue: 2 Dated: (APRIL 1980) Pages: 241-272
Date Published
1980
Length
32 pages
Annotation
THIS ARTICLE INTRODUCES AND APPLIES THE PEARSON SYSTEM OF FREQUENCY CURVES. THIS SYSTEM CAN IDENTIFY A WIDE RANGE OF SKEWED STATISTICAL DISTRIBUTIONS USING EMPIRICAL DATA.
Abstract
IN APPLIED RESEARCH, SOCIAL SCIENTISTS MUST DETERMINE WHETHER THE ASSUMPTION OF NORMALITY OF DISTRIBUTION IS REASONABLE. GIVEN THAT SOCIOLOGICAL PHENOMENA (INCOME, EDUCATION, OCCUPATION, ETC.) ARE MORE LIKELY TO CONFORM TO VARIOUS TYPES OF SKEWED DISTRIBUTIONS THAN TO THE NORMAL ONE, IT IS METHODOLOGICALLY ADVANTAGEOUS TO IDENTIFY A SPECIFIC SKEWED DISTRIBUTION WHICH CONFORMS TO A STATISTICAL DISTRIBUTION. PEARSON SUGGESTED THAT IT IS USUALLY SUFFICIENTLY ACCURATE TO ESTIMATE CURVES BASED ON SECOND-DEGREE POLYNOMIALS. PEARSON'S SYSTEM HAS THREE MAIN TYPES OF FREQUENCY CURVES AND CAN SIGNIFICANTLY HELP IN SOCIAL RESEARCH. A POPULATION DISTRIBUTION COULD BE COMPARED WITH A SAMPLE DISTRIBUTION OR REPEATED SAMPLES COULD BE ANALYZED TO ESTIMATE THE PARENT DISTRIBUTION. IDENTIFICATION OF THE DISTRIBUTION COULD ACCURATELY REVEAL THE DISTRIBUTION'S MODE AND THE PROBABILITY OF OCCURRENCE OF A SOCIOLOGICAL EVENT GIVEN A CERTAIN RANGE OF THE INDEPENDENT VARIABLE. SOME DISTRIBUTIONS ARE BIMODAL, HOWEVER, AND THEREFORE LESS LIKELY TO CONFORM TO A STATISTICAL DISTRIBUTION. IN MANY CASES ALL BUT ONE OF THE DISTRIBUTION'S CATEGORIES COMFORM TO A SPECIFIC DISTRIBUTION. A CATEGORY'S DEVIATION FROM THE DISTRIBUTION COULD BE INVESTIGATED. IDENTIFICATION OF A STATISTICAL DISTRIBUTION PROVIDES OBJECTIVE CRITERIA FOR EVALUATING FUTURE RESEARCH FINDINGS, WHICH COULD CLASSIFY SOCIODEMOGRAPHIC DISTRIBUTIONS INTO VARIOUS TYPES OF STATISTICAL DISTRIBUTIONS. NOTES, ILLUSTRATIVE EXAMPLES, TABLES, FIGURES, A REFERENCE LIST, AND APPENDIXES PRESENTING MATHEMATICAL DETAILS OF THE METHOD, ARE INCLUDED. (CFW)