The law requires coal mine operators to test the amount of dust in the atmospher

Question

The law requires coal mine operators to test the amount of dust in the atmosphere of the mine. A laboratory carries out the test by weighing filters that have been exposed to the air in the mine. The test has a standard deviation of = 0.12 milligram in repeated weighings of the same filter. The laboratory weighs each filter four times and reports the mean result.

a. What is the standard deviation of the reported result?

b. Why do you think the laboratory reported a result based on the mean of four weighings instead of just one?

Explanation / Answer

standard deviation of the reported result =population std deviation/(n)1/2 where n=4

=0.06

b)as there single weighing result can contain error factor due to different lurking variables the mean of larger number of values will be near to actual value of wright due to law of large numbers

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