"Note also that the original data set (if there were one) should probably be analyzed as a time series with a 1-week cyclic component.
-Robert Dawson" Yes, I ignored this possibility in trying to get the right null. But if the data is not handled properly doesn't matter what the null is, the results are incorrect. Michael **************************************************** Michael Granaas [EMAIL PROTECTED] Assoc. Prof. Phone: 605 677 5295 Dept. of Psychology FAX: 605 677 3195 University of South Dakota 414 E. Clark St. Vermillion, SD 57069 ***************************************************** ----- Original Message ----- From: "Robert J. MacG. Dawson" <[EMAIL PROTECTED]> Date: Tuesday, February 24, 2004 12:54 pm Subject: Re: [edstat] question on hypothesis testing > It was asked: > > > How would you test the following hypothesis: > > A fast-food restaurant claims that 75% of their revenue is from the > > "drive-thru". Suppose you have 50 days of receipts from the > > restaurant. Each days' receipt shows the total revenue and the > > "drive-thru" revenue for that day. > > and various people responded (eg): > > compute the proportion from the drive through for each > day, and > > then test if that were 75%. Then, instead of two numbers for > each day, > > you have only one, > > Yes... > > > and that's the one you're interested in. > > No, it isn't! The mean of the daily proportions is not in > general the > same thing as the overall mean. This is closely related to Simpson's > paradox. > > Drive Table Proprortion > through DT > > Tue 30 10 .75 > Wed 30 10 .75 > Thu 30 10 .75 > Fri 30 90 .25 > Sat 30 90 .25 > Sun 30 90 .25 > ___________________________ > # 0.5 > ======= > Total 180 300 | 0.375 > > Note also that the original data set (if there were one) should > probably be analyzed as a time series with a 1-week cyclic component. > > -Robert Dawson > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
