This book focuses on analyzing the validity of questionnaire items for evaluating supermarkets from the point of view of their customers. Twenty-four evaluation items related to supermarket services were selected to create a questionnaire, which was answered by customers of the establishment studied, evaluating each item as essential, important, but not essential or non-essential. Applying the Lawshe method, it was possible to validate or exclude items from the questionnaire according to the perception of the respondents.