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Discussion Groups / English Usage / January 2009representative cross-section vs random cross-section
Hello! I would like to know if the two expressions are both possible, "a representative cross-section of the English population" and "a random cross-section of the English population". Thank you in advance. LP >Hello! I would like to know if the two expressions are both possible, >"a representative cross-section of the English population" and "a >random cross-section of the English population". A cross-section, when it used to describe statistics, means a sample meant to be a representation of the whole. So, "a representative cross-section..." is a tautology and shouldn't be used. All statistical samples are taken at random, so a "random cross-section" is a tautology and shouldn't be used.  SignatureTony Cooper - Orlando, Florida I looked for examples of both expressions on Google, and found that there are infinite number of "a representative cross-section", while only one example of "a random cross-section" whose context I cannot make sure. While "a representative cross-section" is a tautology, I wonder if you can randomly choose "a sample that should represent the whole" without deliberate choice. LP >>Hello! I would like to know if the two expressions are both possible, >>"a representative cross-section of the English population" and "a [quoted text clipped - 5 lines] > statistical samples are taken at random, so a "random cross-section" > is a tautology and shouldn't be used. While that is the ideal situation, in practice getting a truly representative cross-section may require pre-screening that reduces the randomness of the sample. If I'm trying to get a representative cross- section of cat-food purchasers, I will be wasting time, effort, and money if I don't screen out those people who do not now, and never have, owned a cat. >>>Hello! I would like to know if the two expressions are both possible, >>>"a representative cross-section of the English population" and "a [quoted text clipped - 12 lines] >if I don't screen out those people who do not now, and never have, owned a >cat. You still do a random sample. You limit the universe to cat owners, but you don't select the *particular* cat owners. In this case, you might approach people leaving a store like PetsMart and ask them if they own a cat. If the answer is "Yes", you use them in the sample. What you don't do is further select to pick out a characteristic of the person that you feel would make a good responder. A sample universe is not everyone who walks by. It is the people who walk by, randomly selected, who meet the objectives of the survey. If you are establishing tampon brand preference, naturally you are going to make the random selections from a limited universe of females within a certain age range. Pre-qualifying your universe does not take away the random aspect. It just makes your universe a sub-section of the total universe. You can also post-qualify by asking age and preferred brand, and then throw out those above or below the age bracket involved. What's left is still a random selection if you ask all females walking by. SignatureTony Cooper - Orlando, Florida Both expressions (to me) seem to be correct usages of grammer, however the terminology used can be ambiguous in its meaning. A 'random' cross section is a contridiction in terms as a 'cross section' as mentioned by others is a statistical term which implies the 'representative' view of a subject rendering the phrase "random cross-section" as contradictory in nature. The implication of such a usage would be that even though the view is representative, it is still taken from a random sampling of the subset 'representative'. My personal viewpoint would be that additional qualifications would be needed to use either phrase without a perception of laziness in the actual usage, and that a more precise phrase might be "random subset of a known cross- section". >Hello! I would like to know if the two expressions are both possible, >"a representative cross-section of the English population" and "a [quoted text clipped - 3 lines] > >LP |
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