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Comparing two means

  1. Mar 21, 2007 #1
    It's sort of a conceptual question:
    one of the assumptions for 2-sample t confidence interval is equality of variances in two populations, and I need to come up with a concrete example of when this is likely to fail.
    I sort of have an idea that it really depends how one chooses samples. For example, if one compares mean hight of males and females on a certain campus where females are predominantly asian. Then since variance in hight of asian women is much smaller than variance in hight of white males, the assumption fails. ALthough I am not sure if this is a good example because I make an explicit assumption that asian females have small variance in height. Could someone help me out a bit with an example?
    Thanks in advance.
     
  2. jcsd
  3. Mar 21, 2007 #2
    When what is likely to fail?
     
  4. Mar 21, 2007 #3
    equality of the variances of the 2 populations
     
  5. Mar 21, 2007 #4
    The probability of the two variances being equal is exactly zero.
     
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