Talk:Sampling (statistics)

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A question that's been bothering me for some time: how does population size affect sample size for the same probability of precision? (I hope I asked this correctly.) Wblakesx

The proportion of sample size to population size is called the sampling fraction. Generally speaking, the precision depends on the absolute number of samples, taken and NOT the sampling fraction. Thus a sample of random of 1000 people is fine for estimating the views of a population of 60 million (as in the UK) but it would be almost equally good for estimating the views of a population of 600 million of 6 billion. Having said that, it's not quite true. As the sampling fraction becomes significant (greater than 5 or 10%, say) you do need to add a correction to your precision estimates. But it's a good question, because the layman's intuition that the sampling fraction must be large for the sample to be good is dead wrong! Blaise 22:09, 20 September 2005 (UTC)

What is random sampling ?


The first line of the Mechanical Sampling section reads:

Mechanical sampling does not occurs typically in sampling solids, liquids and gases, using devices such as grabs, scoops, thief probes, the coliwasa and riffle splitter.

This doesn't make any sense. I don't know anything about mechanical sampling so could someone who does please fix this? TooMuchMath 03:06, 15 May 2006 (UTC)

Contents

[edit] Indian invention of sampling in 1928

User:144.92.82.172 added this statement to the article: "Some say that sampling was invented in India in July 1928." Can anyone provide a source explaining this claim? I have removed it from the article for now. -- Avenue 13:17, 25 May 2006 (UTC)

This claim does not proceed; Sampling is a intuitive concept and happens (by instinct) since the beggining of time. Also, there are records of use of previously planned samples since the XIX century.--Lucas Gallindo 20:06, 29 September 2006 (UTC)


Sampling is mentioned in the Bible.

[1] Now the leaders of the people lived in Jerusalem; and the rest of the people cast lots to bring one out of ten to live in Jerusalem the holy city, while nine tenths remained in the other towns.

Nehemiah 11. 1

Blaise 09:51, 16 February 2007 (UTC)

[edit] Section on case studies and sampling

Editors Krakenflies and Gsaup recently added this extensive section on "sampling" in case studies. Although I enjoyed reading the linked article, I believe the section does not relate to the topic of this article, statistical sampling, so I will delete it. Perhaps it could go in a new Sampling (case studies) article instead. -- Avenue 11:51, 11 August 2006 (UTC)

Or maybe combined with Theoretical sampling? -- Avenue 12:09, 11 August 2006 (UTC)

[edit] Added definitions for types of data and levels of measurement.

I thought these subheadings would be relevant. Let me know. JT Pickering 22:20, 3 September 2006 (UTC)joe pickering

[edit] Outdented 'levels of measurement'

Seemed to flow better when not considered as part of the types of data.JT Pickering 18:29, 12 November 2006 (UTC)

[edit] Sampling used as Democratic Process

I would like to know of any movements, if they exist or ever have existed, which advocate for the use of random sampling techniques to provide official decision making bodies. For example, what if the US House of Representatives were actually a representative sample? This seems like something which could be worthy of exploration since it seems one of the only ways to remove bias toward the rich and the non-competitive climate would almost certainly be more conducive to productive intellectual dialogues, as opposed to degenerate partisan contests. Maybe then politics wouldn't be such a turn off to so many people. LordBrain 23:21, 6 October 2006 (UTC)

I believe the phrase is 'government by lot.' To my knowledge, it's never been a primary governmental method, but it does show up here and there in different ways. In the US, the most prominent example is jury duty. The problem--jury duty is a good example--is that it is extraordinarily vulnerable to manipulation. In any event, it shouldn't really be included in this article. Ethan Mitchell 20:00, 22 January 2007 (UTC)

[edit] Stratified sampling

At the end of the Stratified sampling section it says:

"Typically, strata should be chosen to have:

   * means which differ substantially from one another
   * variances which are different from one another, and lower than the overall variance."

Wouldn't the second bullet be more clearly expressed as "minimise variance within strata and maximise variance between strata."?

It might also be worth mentioning that stratified sampling can introduce bias when selecting strata.

[edit] Selective Sampling

There is no mention of selective sampling! -- Flutefluteflute Talk Contributions 11:31, 29 March 2007 (UTC)

I don't know much about selective sampling, but I gather from skimming these articles [1] [2] [3] that it is a machine learning term for techniques for selecting your sample to reduce the numbers needed to get good predictions, i.e. it would be part of experimental design (specifically adaptive designs) rather than sampling in the usual statistical sense. If I'm right, it wouldn't hurt to add a note to that effect. -- Avenue 13:34, 29 March 2007 (UTC)

[edit] Section on Graduate degree programs specializing in sampling/survey methods

How is this section relevant to the rest of the article? It merely contains links with no further description. It is even placed after the See Also section. I suggest removing it. Mdanh2002 (talk) 16:00, 9 April 2008 (UTC)

I agree entirely so I have removed it in line with WP:EL. Qwfp (talk) 17:33, 9 April 2008 (UTC)

[edit] Types of data

I think that this section might be improved (generalised). A link to Level of measurement might be worthwhile anyway. There may be some question about how much needs to be in the present article, but something about ordinal data (at least) seems necessary here. Melcombe (talk) 09:47, 15 April 2008 (UTC)

I think that section doesn't really belong in this article. How about we move it to Statistical survey? I agree it could be improved. -- Avenue (talk) 12:35, 16 April 2008 (UTC)