HW#11
Nov 20, 2006
E1)
(a) The way the manufacturer set up the hypothesis test put the burden of proof on
the MPG being less than 30, when the burden of proof should really be on it being
greater than or equal to 30.
(b) Given that the average of the sample data was itself less than 30, it is wrong to
claim that the true mean is greater than 30 with a reasonable level of confidence.
E2)
This conclusion is based on the fact that in the real world nothing can be determined
with 100% confidence. However, they are incorrect stating that statisticians are wrong
5% of the time because that 5% is accounted for in a 95% confidence interval.
E3)
Statistical significance measures unlikeliness that deviations from mean are due to
coincidence, whereas practical significance asks if the differences are large enough to be
practical. For example, a sample average of 101
for many observations
would yield a
very small pvalue based on a presumed true mean of 100. However, the difference may
not be significant in practical terms and one may not wish to reject such small deviations.
44)
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 Fall '08
 Stedinger
 Statistics, Statistical hypothesis testing, Statistical significance, 3%, µs, true mean

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