Rich Ulrich wrote: > For the point assertion, I would take the two subtotals > for the 50 days, and ask, "Is this one 3 times that one?" > Is that a test, or an assertion of the-state-of-the-world? > > Do you want to know whether it is true every week? > - then take weekly totals. That gives you seven weeks. > The claim about "75%" might be shown to depend on > other contingencies or chance; or might not. > > Taking 50 days separately is not very necessary, since > it is not (I think) primary to the claim. However, it could > be an additional point of convincing evidence, if the > assertion were true (almost always) on that daily basis. > > For a statistical assertion about the proportion, I would > probably use the weekly ones -- not nearly the accidental > changes owing to days, or the day-to-day autocorrelation > in whatever is going on.
I think the most reasonable meaning is that the annual revenue is 75% drive-thru - so there probably aren't enough data to assess this claim. The daily totals will obviously be biased (and one would hope the weekly totals are less biased as they should even out week-day vs. weekend demand, but there will also probably be seasonal biases). Thom . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
