Here you find R code, which is used for the development and validation of measurement instruments (questionnaires, tests, items, scales) for the social sciences. The description of the analyses carried out with the codes can be found in the appendices A1 to A5 of the ZIS Publication Guide. Each code includes comments to guide users through the code. We provide the data set “example1” to run the code. We provide: Code for testing the dimensionality of scales comprises exploratory factor analysis, principal component analysis, and confirmatory factor analysis (tau-congeneric and tau-equivalent). For the description of the analyses, see appendices A1 to A2 of the ZIS Publication Guide. Code used to estimate reliability comprises the estimation of split-half reliability, retest reliability, reliability coefficients for single-factor models (Cronbach’s Alpha, McDonald’s Omega/Raykov’s Rho, AVE [Average Variance Extracted]), and bi-factor models (Omega-H, ECV [Explained Common Variance]). For the description of the analyses, see appendix A3 of the ZIS Publication Guide. Code for measurement invariance testing within SEM. For the description of the analyses see appendix A5 of the ZIS Publication Guide.