| Chi-square is a convenient measure of
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| | doesn't have a brain. It is merely an
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| association between two factors when the
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| | algorithm of human frequencies, a
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| factors are not quantitative. It
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| | mechanical process based on numbers
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| indicates the degree to which the human
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| | regardless of what they represent. By
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| frequencies in a cross-tab of the two
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| | itself, it never can take the place of a
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| factors deviate from what they would be
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| | regression or correlation because it
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| if there was no interrelation at all
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| | cannot describe the human frequencies,
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| between the factors. The computed
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| | only gauge their statistical
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| chi-square has a specific level of
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| | significance, entirely regardless of
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| statistical significance looked up in a
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| | logic or sense.
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| standard table.
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| | Chi-square is non-parametric. To describe
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| Suppose we ask 300 testers to rate our
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| | a human frequency in numerical terms, we
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| pretzels (A) and another brand's (B) both
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| | need numerical values-that is,
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| in terms of overall preference and
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| | parameters. If we arbitrarily assign
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| preference regarding human frequencies.
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| | value +1 to preference for A and -1 to
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| By a convenient coincidence, the "crunch"
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| | preference for B, we can compute a
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| preference divides exactly even, with 100
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| | correlation coefficient-r= +.246 for the
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| preferring A, 100 preferring B, and 100
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| | original tabulation, and exactly half
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| having no preference.
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| | that for the corrected distribution. The
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| Clearly, there is a strong association
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| | parametric regression/correlation, unlike
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| between the preference on "crunch" and
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| | chisquare, is affected by the way the
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| overall human frequencies; chi-square is
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| | rows and columns are labeled because each
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| 18.4, indicating a significance level of
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| | label has a specific value.
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| 99%+ ... Wait a minute, there's the
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| | So chi-square is a very useful index when
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| phone. What's that? I see... a
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| | we cannot assign values to human
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| stub-labeling error, the last two lines
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| | frequencies, but it is very easy to
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| got switched... Okay, thanks.
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| | misuse it; it doesn't have a brain, so
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| So let's see, now we have:
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| | the analyst has to use his or her own
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| That still looks like a strong
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| | brain to interpret it correctly.
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| association for (A) but not for (B), so
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| | Though one doesn't necessarily need fancy
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| we should have a lower chi-square, right?
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| | testing equipment to know how they feel
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| No. Chi-square is still 18.4. As long as
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| | health-wise. Once the human body can
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| the numbers stay the same, it doesn't
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| | absorb the right nutrition in the correct
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| matter how they are labeled. Like the
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| | electrical patterns, health can't help
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| Scarecrow in Wizard of Oz, chi-square
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| | but improve.
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