Dr. Jennings is interested in whether or not the types of plants (aquatic, semi-

Question

Dr. Jennings is interested in whether or not the types of plants (aquatic, semi-aquatic, non-aquatic) found in the James River Park System vary by environment types. She takes simple random samples from each of the marshy areas, simple random samples from each of the meadow areas, and simple random samples from each of the wooded areas. Her data are as follows: aquatic semi-aquatic non-aquatic marsh 10 8 2 meadow 0 2 18 woodland 0 0 20 a) What type of sampling was this? b) According to the data, does it appear that the types of plants vary by environment type?

Explanation / Answer

This is stratified random sampling. If the population is heterogeneous, then simple random sampling is not applicable directly. Therefore the heterogeneous population is divided ito various strata( groups) within which the elements are homogeneous. Here James river oark system is heterogeneous population which is divided into three strata viz aquatic , semiaquatic & non aquatic within which the elements are homogeneous as per the environmental conditions. Thus from each stratum then simple random samples are drawn of given size which is proportional to the stratum size, where strata are regarded as subpopulations.

Yes of course, according to data , it does appear that the type of plants vary by environment type, as trees grow as per the environmental conditions.

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