Which characteristic is NOT used to form strata in the described stratified sampling?

Which characteristic is NOT used to form strata in the described stratified sampling?

• A. Race/ethnicity
• B. Free lunch status
• C. Gender
• D. Favorite color

Answer: (D)

Stratified sampling aims to ensure representation across important subgroups by dividing the population into nonoverlapping, homogeneous groups and sampling from each group. The traits used to create these strata should be related to the variables of interest or known sources of variation, so that differences between groups matter for the study and the sampling precision improves. Race/ethnicity and gender are common strata because they often correspond to meaningful differences in experiences or outcomes. Free lunch status serves as a proxy for socioeconomic status, which can influence many educational or behavioral variables. Favorite color, on the other hand, is arbitrary and not tied to demographic, socioeconomic, or study-related differences; forming strata around it would not enhance representativeness or precision and would add unnecessary complexity.

Stratified sampling aims to ensure representation across important subgroups by dividing the population into nonoverlapping, homogeneous groups and sampling from each group. The traits used to create these strata should be related to the variables of interest or known sources of variation, so that differences between groups matter for the study and the sampling precision improves. Race/ethnicity and gender are common strata because they often correspond to meaningful differences in experiences or outcomes. Free lunch status serves as a proxy for socioeconomic status, which can influence many educational or behavioral variables. Favorite color, on the other hand, is arbitrary and not tied to demographic, socioeconomic, or study-related differences; forming strata around it would not enhance representativeness or precision and would add unnecessary complexity.