This article discusses the history and application of Cochran's sample size formula in statistics. It explains how the formula is used to calculate the ideal sample size for different populations and provides insights into its accuracy and applicability. The article also explores the use of the Kaiser-Meyer-Olkin (KMO) measure in factor analysis and the concept of regressive analysis in SPSS. Additionally, it provides a step-by-step guide on how to run Confirmatory Factor Analysis (CFA) in SPSS.