In summary, the Conners 4 Normative Samples are representative of the U.S. and Canadian populations. The Normative Samples each contain proportions of the key target demographic variables described in this chapter (i.e., gender, race/ethnicity, region, and PEL) that are consistent with U.S. and Canadian census proportions. Furthermore, the Conners 4 Normative Samples contain proportions of youth with a clinical diagnosis in accordance with recent prevalence rates to better reflect the actual general population, which includes youth with and without clinical conditions. Additionally, ADHD Reference Samples were collected to represent youth with ADHD, including those with co-occurring clinical diagnoses. Detailed information about the raters in all samples are provided and reflect a diverse population. Using these standardization samples, standardized scores were computed to convert raw scores into T-score and percentiles that account for the age of the youth being rated, as well as standardized scores that can also account for the youth’s gender, if desired. Empirical percentiles were calculated to accurately describe the skewed shape of the distribution of many of the Conners 4 scales for the Normative Samples, and theoretical percentiles were calculated for the ADHD Reference Samples.