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Re: Exam Reply
Posted:
May 8, 1997 8:27 AM


From Kevin Rees: >the >AP exam questions give you FAR more information than >you need in order to determine whether or not the student >understands the situation of the experiment. >Question #5 gave sample statistics for each sample and >for the differences, about 95% of my students correctly >choose to ignore the statistics for the differences as two >different ovens are "assumed" to be independent (yes they >could be connected to the same power source, be next to >each other, etc. yet without more in the question it seems >more appropriate to treat them as independent). >I am assuming that when the test is graded they will be >looking for twoindependent sample analysis rather than >dependent samples analysis and will grade accordingly.
Kevin What I found most interesting about question #5 was the decrease in % of defective chips over time in both ovens. Time is ovbiously important, and it raises the question of whether or not the "population" of % defective chips is normally distributed (a normal quantile plot of Oven A's output is not particularly linear). My initial reaction to the problem was to lean toward doing matchedpairs on the hourly differences to eliminate the issue of time, but I didn't think about the problem of independence. (I haven't met with my students yet, so I don't know what they did). How big a problem is that? Shows how much I don't know.
Tim Brown Lawrenceville School Lawrenceville, NJ



