Qisqacha mazmuni. This paper explores the significance of Cronbach's alpha in evaluating the internal consistency and reliability of test scores, particularly in educational assessments. Through a comprehensive analysis, we highlight how closely the response matrix of test results aligns with the Guttman pattern, emphasizing the importance of the number of items when making inferences using Cronbach's alpha. We conducted a field test with 423 students to evaluate a newly developed biology assessment tool, ensuring the reliability and validity of the test through robust statistical methods. The study presents a detailed examination of the Guttman pattern, its implications for test analysis, and the interpretation of Cronbach's alpha in different test scenarios. We also compare the descriptive statistics and reliability measures of simulated data sets with normal distribution and actual test data, providing insights into the practical applications and limitations of Cronbach's alpha in real-world settings. The findings underscore the importance of careful item selection and test design to enhance the reliability and interpretability of educational assessments

Kalit so'zlar. Assessment, classical test theory, achievement tests