Sampling Methods

[charikaar]

Hello,

This forum seems very helpful. Could somebody spare sometime and help me with this question.

What are different type of sampling?

I know some of them random sampling,stratfield sampling etcc but I don't whats the definition. could you please give me definition for these along with some others.



Thank You.


Charikaar

[JBL]

Hi there. The forum you have posted this in is for beginning problem solvers in middle school. Your question would probably belong much better in the "Other Problem Solving Topics" forum of the High School section of this site.

One definition of sampling (from mathworld.wolfram.com , an exceptionally useful site) is "In statistics, sampling is the selection and implementation of statistical observations in order to estimate properties of an underlying population." However, you really need someone who knows more statistics than I to answer this question for you.

[Bictor717]

Simple random sampling is choosing names out of a hat. An equivalent is assigning each experimental unit a number and use a random numbr generator to choose the units. Each unit has the same chance of being chosen and each n-sized group has the same chance of being chosen.
Stratified random sampling is dividing your experimental units into groups (stratas) and then applying the simple random sample to each group. You can have a stratified random where each unit has the same chance of being chosen, but each n-sized group can never have the same chance of being chosen.
An example:
Say there are 100 boys and 150 girls. If you divide them into groups according to their gender and pick 10 boys and 15 girls, each person has a 1/10 chance of being chosen. But it is impossible for you to pick anything other than 10 boys and 15 girls, like all boys. This is a stratified random sample.
However, if you put all the names of the boys and girls in a hat, and randomly pick 25 names out of the hat, this is a simple random sample, since each person has the same chance of being chosen and each 25 person group is equally likely to occur.
The other two I know of are systematic random sampling and multistage random sampling.
In systematic random sampling, you say in advance what system you use, like picking every tenth person, and use a simple random sample to pick the first. From the example above, say you list the names alphabetically, and you pick one person with a simple random sample. Then to get a sample of 25 people, you would take that person and every tenth person on the list after him/her. If you picked the 4th person, then your sample would be the 4th, 14th, 24th,...,244th.
Multistage random sampling involves using a simple random sample many times to choose a small sample from a large population.

[A MATH]

I'm moving this, you can probably get more answers at Other Problem Solving Topics.

[charikaar]

Hello,

Thanks for your replies. I am pretty new to this forum and didn't know where to post.


I am sorry to have cause you any inconvenience.



Charikaar