## Class 28: Psychokenesis, continued

### Discussion

We will continue the discussion of psychokenesis and the PEAR lab, starting with the following questions from last time.

In these experiments the researchers did not try to control the number of times a subject could participate. If there was a tendency for subjects who succeeded in one session to try again would this make it more likely that the results would be significantly different than by chance? Answer the same question if they were allowed to quit at any time during the session.

At a recent gambling conference a Casino owner made the following remark: If we took the 0's off the roulette wheel, we would still make all kinds of money since most gamblers would still come in and play until they have lost their money and then leave. What do you think?

Has the PEAR lab changed your opinion about ESP? What would the PEAR lab have to do in order to a) make you a believer, if you are not already, b) convince the scientific community, and c) convince the general population?

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Here's a probability paradox to think about.

Your uncle presents you with two sealed envelopes on your birthday, and tells you each of them contains a check. He says that one check is for twice as much money as the other, and lets you chose which envelope you want. You make your choice and find that the check inside is for $20.

Your uncle now asks you if you would like to switch envelopes. Having taken an introductory statistics class, you reason as follows. The other envelope is equally likely to contain $40 or $10. Therefore, the expected value for the other envelope is ($40 + $10)/2, or $25. Should you switch?

### Journal Assignment

Read the article "New estimates in old debate on Internet Use" from today's *NY Times* (April 17, 1996). Find out as much as you can about how the same data was used to get such wildly different estimates. In particular, what is the weighting system referred to by *the New York Times* article. Why were weightings used? Where do you think the truth lies in all these estimates? One source of information about this debate is the Web itself. The article mentions a report posted by the Professors Hoffman and Novak last Friday. We'll give an extra 2 journal points to the first person who finds and tells us the Web address of this report.