This is the description of the sample plan for a survey of enrollments by mail questionnaire of 1800 colleges and universities in the United States. The requirements of the survey included speed, ...

Suppose that the sample of students described in the previous section was actually selected using stratified random sampling. In stratified sampling, the study population is divided into ...

Suppose that the previous student sample is actually drawn from a stratified sampling. The strata are grades in the junior high school: the 7th grade, the 8th grade, and the 9th grade. Within strata, ...

Objective: To study the predictive power of serum selenium with regard to cancer mortality in a large sample of the Belgian population given the lack of coherence in the results of observational ...