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Unformatted text preview: 1 Statistics We have a set of N measurements of some quantity x . The measurements are x 1 , x 2 , ... x N . The values are not all the same because of errors that we cannot control. The picture below shows the measured electrical current through a series of meters. They should all display the same value and they do not. How do we decide what the real value is, and how reliable is our estimate of the real value? There are two issues here Our answer could be very close to the right answer (its accurate) Our answer could only be in a very small range (its precise) In a real experiment, you can be lucky and get an accurate answer and it may or may not be precise. Also, you can be unlucky and get an inaccurate answer, and it may be precise or imprecise. We will always have an uncertainty in our measurements. Therefore we cannot quote a single value, but only a range of values. We write x for our answer, meaning we believe the real answer is in the range of ( x- , x + ). For example, if we believe the actual mass of an object is in the range of 2.9g to 3.1g we would write that as 3 . . 1 g....
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This note was uploaded on 11/23/2011 for the course PHYS 6198 taught by Professor Cohor during the Summer '10 term at LSU.
- Summer '10