Background: The appropriate validation of analytical methods has become an essential part of the determination of chemical substances. Invalid analytical methods lead to inaccurate data and misinterpretation of results in the pharmaceutical, food, and medical sciences. There are a number of guidelines issued on validation by international organizations. Some parameters have been proposed to evaluate the validity of an analytical method. They are accurate and comprehensive; however, proposing new criteria can help analysts to detect invalid methods. Objective: In this study, new criteria are proposed based on upper and lower limits of linear range and calculated responses by calibration curve equation. Methods: Further research on 150 reported analytical methods (non–separation-based and separation-based techniques) for chemicals and pharmaceuticals (organic and inorganic compounds) in scientific papers revealed that employing the coefficient of determination (R²) alone could lead analysts to an inaccurate linear range and method validation, and consequently, results showed that only 55% of these methods count as valid approaches. Conclusions: The established criteria based on the calibration curve equation and linear range appear to be applicable and suitable for validity evaluation of analytical methods.