11&12 please

11) What is one advantage ofstratified random sampling over simple random sampling? A) It allows you to select specific groups to include and exclude to sample from B) You get less bias in the sample withstratified random sampling. C) It combines the best of cluster sampling and simple random sampling because of omited variable D) Stratified random sampling ensures that at least 1 person from each group will be in the sample. bias. 12) Selection bias occurs when A) cluster sampling is used instead of stratified random sampling B) portions of the population are excluded from the consideration for the sample those responding to a survey or poll differ systematically from the nonrespondents D) the population has been divided into strata