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Re: [Phys-l] Data Analysis Questions



Hugh,
We use Wavetek 25 and 27XT digital multimeters not a bridge. I don't know that I believe that last digit (on the multimeter Wavetek promises 0.5% of the reading) but for the purposes of the lab, it works. The thrust of the lab is to show that the two resistor populations are different and to show how rejecting a Null Hypothesis works. We tried to relate it a real world situation as the prolog of the lab shows:

" So let us consider a scenario: You are the manufacturer of an electrical device that uses 100 ohm resistors. The vendor for the resistors has just introduced a new "improved" version of the 100-ohm resistor that costs less. The question that you are facing: Should you take advantage of the cost savings and replace the old resistor with the new improved version?

Actually, that is a pretty antiseptic version of the problem. Let's rephrase the problem. You are a manufacturer of heart pacemakers for implantation in humans. Should you put the new resistor in the pacemaker in place of the old one? Keep in mind that resistors cost about a penny apiece when bought in bulk. One successful lawsuit against you will wipe out any economic gains for several centuries.

Better yet, it's YOUR pacemaker that the resistor will go in.

Welcome to measurement in the real world. The question that we want to investigate is very straightforward to state and nigh onto impossible to prove: Are two populations the same? Already we have a problem because the question needs to be rephrased: Is some measured quantity the same for two populations?....

I will spare you the rest.

---- Original message ----
Date: Fri, 28 Nov 2008 15:51:44 -0500
From: Hugh Haskell <hhaskell@mindspring.com>
Subject: Re: [Phys-l] Data Analysis Questions
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>

Sounds like your resistors are all from the 1% (gold tolerance band)
stock. I guess that would be the best way to do this exercise. Are
you measuring the resistance with a bridge to get it that accurately?
I don't recall our digital V-A meters giving that precision.

Hugh
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