Nominal level of measurement refers to a classification system in which data are grouped into categories without any order or ranking. The categories are mutually exclusive and each item belongs to only one category. Numbers assigned to nominal data are used only as labels and have no mathematical value. This level of measurement is commonly used in nursing research for identifying and grouping subjects according to specific characteristics. Characteristics of nominal level measurement include: * Data are categorized by name or label. * Categories have no numerical significance. * No order or ranking exists among categories. * Mathematical calculations such as mean and standard deviation cannot be applied. Examples in nursing education and research: * Gender of patients: male, female, transgender. * Blood groups: A, B, AB, O. * Marital status: single, married, divorced, widowed. * Type of disease: diabetes, hypertension, asthma. * Religion of patients or students. For example, in a nursing research study investigating the prevalence of hypertension among male and female patients, gender is measured at the nominal level because it simply classifies participants into categories. Ordinal level of measurement refers to data that can be arranged or ranked in a meaningful order, but the intervals between ranks are not equal or measurable. It provides information about relative position rather than exact differences between values. Characteristics of ordinal level measurement include: * Data are arranged in order or rank. * Categories indicate greater or lesser degree. * Differences between categories