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Topic: correlation
Replies: 0

 Peter Bruce Posts: 10 Registered: 12/6/04
correlation
Posted: Oct 3, 1996 2:48 PM

[I tried to post this earlier & think I failed; my apologies if I'm
repeating it. The original query sought a good exercise on probability, and
various responses came in with suggestions for problems or data to use.]

> To any of the other fine suggestions that responded to this post, add a
> segment on probability. Confine the data to 10 cases, and calculate r.
>
> Next, arrange a deck of cards so that you have only the numberd hearts
> (ace-10) and numbered spades. Shuffle the cards and deal them out. Ask
> what you would expect -- best guess -- the correlation to be between the
> values of the two suits. Now calculate it. Do it a couple of times.
>
> To move things more quickly do it on the computer. Here are Resampling
> Stats commands; I'm sure this could be done in other packages as well:
>
> DATA 1,10 hearts
> SHUFFLE hearts hearts*
> PRINT r
>
> After doing it a number of times, ask students to explain how the cards can
> produce substantial positive and negative correlations (10% of the results
> will be >.5 or < -.5).
>
> Now do the cards example lots of times.
>
> DATA 1,10 hearts
> REPEAT 1000
> SHUFFLE hearts hearts*
> SCORE r z
> END
> HISTOGRAM z
>
> Observe the distribution of the r produced by random shufflings.
>
> Ask them to interpret the observed value in light of these data.
>
> (note: it helps to have the 10 real cases with observed "r" is between .3
> and .45 -- big enough to suggest a relationship, but small enough to come
> within the range of chance variation)
>
>
> Peter Bruce
>
>
> At 04:46 PM 9/30/96 -0400, you wrote:

> >Note: this is a serious request, and not a joke.
> >
> >If you were informed that a ranking official from the federal government
> >was going to visit your AP Stat class while you were doing a unit on
> >correlation, what activity would you do? All suggestions welcome, and any
> >one I use will receive proper credit refernces. Thanks in advance.
> >
> >Chuck

Peter Bruce voice 703-522-2713
Resampling Stats fax 703-522-5846
612 N. Jackson St. stats@resample.com
Arlington, VA 22201 www.statistics.com