#### • Class 11 Physics Demo

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#### • difference between stratified and cluster sampling

Question:In probability and statistics, what are the advantages and disadvantages of stratified sampling over random sampling?

Answers:The wiki (ref) lists four advantages and five disadvantages. The main advantage of stratified sampling is that you guarantee a balanced sample. The disadvantage of stratified sampling is that it's harder to do. One way to get the benefits of both is to take a random sample, and then weight your results based on your demographics. But if you under-sample a large group, your statistical uncertainty can go way up.

Question:a principle wants to survey the student body about the convenience and security of the student parking lot. the statistics teacher recommended a stratified samole, but the got interrupted before he could explain what that meant. decide what factor the principal should use to stratify and explain how the principal could produce a stratified sample with 100 students.

Answers:the principle could stratify by grade, by gender, or anything. Then, divide 100 by the number of categories (for example, there are 4 grades in high school), so you would get 25 people in each category to add up to 100.

Question:I have to state reasons why I'm using stratified sampling for my Statistics coursework. Thing is, I'm finding it hard to do that :/ I know it's because you get even and fair proportions from each strata but what are other advantages? If it helps, my coursework is based on a population of students, giving information on their height, their weight. their year group and their gender. Any help is much appreciated.

Answers:Double click on the following website: http://en.wikipedia.org/wiki/Stratified_sampling

Question:I remember learning a formula for working out a stratified sample but I've now forgotten it, and I can't find the formula again. Help!