The article discusses the evaluation of reading ability tests and their reliability. It questions whether tests of reading ability are actually measuring reading ability, despite their reliability coefficients and norms. The study uses two criteria to assess reading ability: one based on teachers' estimates and another based on the combination of tests weighted by their effectiveness in measuring reading ability. The study involved two groups: grade VIII pupils and high school students. Various tests were administered, and their reliability coefficients and correlations with the criteria were calculated. The Terman Group Test of Mental Ability was found to be the most reliable and effective measure of reading ability. The study also found that the Abbott-Trabue Poetic Appreciation test was unreliable for measuring poetic appreciation. The results suggest that tests of reading ability should be evaluated not only by their reliability coefficients but also by their correlation with established criteria. The study warns against the misuse of Spearman's formula and emphasizes the importance of using objective measures to assess the function of a test. The Terman Group Test of Mental Ability was found to be the best measure of reading ability, followed by Thorndike's Visual Vocabulary and Completion tests. The study concludes that tests should be evaluated based on their ability to measure the intended function, not just their reliability coefficients.The article discusses the evaluation of reading ability tests and their reliability. It questions whether tests of reading ability are actually measuring reading ability, despite their reliability coefficients and norms. The study uses two criteria to assess reading ability: one based on teachers' estimates and another based on the combination of tests weighted by their effectiveness in measuring reading ability. The study involved two groups: grade VIII pupils and high school students. Various tests were administered, and their reliability coefficients and correlations with the criteria were calculated. The Terman Group Test of Mental Ability was found to be the most reliable and effective measure of reading ability. The study also found that the Abbott-Trabue Poetic Appreciation test was unreliable for measuring poetic appreciation. The results suggest that tests of reading ability should be evaluated not only by their reliability coefficients but also by their correlation with established criteria. The study warns against the misuse of Spearman's formula and emphasizes the importance of using objective measures to assess the function of a test. The Terman Group Test of Mental Ability was found to be the best measure of reading ability, followed by Thorndike's Visual Vocabulary and Completion tests. The study concludes that tests should be evaluated based on their ability to measure the intended function, not just their reliability coefficients.