Science Sweets and Shooting F09

# Science Sweets and Shooting F09 - Expt 1: Science, Sweets,...

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Expt 1: Science, Sweets, and Shooting Objective To review significant figures rules and understand our expectations. To extend this to accuracy and precision and practical applications, Grading Lab Report (90%) TA points (10%) Before Coming to Lab… Familiarize yourself with the owlspace web page, particularly the resources tab and the connexions tab Introduction In this lab, you will review the rules governing the reporting of significant figures. Some interesting facts about M&Ms: There are approximately 5 calories in each M&M. If you decided to eat a whole a 16-ounce bag, 400 M&Ms (25 M&Ms per ounce), you will need to do the equivalent of nearly four hours of vigorous exercise to work off that many calories. Accuracy Accuracy is how close a measured value is to the actual (true) value . Precision Precision is how close the measured values are to each other . Examples of Precision and Accuracy: Low Accuracy High Precision High Accuracy Low Precision High Accuracy High Precision So, if you are playing soccer and you always hit the left goal post instead of scoring, then you are not accurate, but you are precise!

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Bias (don't let precision fool you!) If you measure something several times and all the values are close, they may still all be wrong if there is a "Bias." Bias is a systematic (built in) error which makes all measurements wrong by a certain amount. Examples of Bias The scales read "1 g" when there is no weight on them You always measure your height wearing shoes with thick soles. A stopwatch that takes half a second to stop when clicked Degree of Accuracy Accuracy depends on the instrument you are measuring with. But as a general rule: The degree of accuracy is half a unit each side of the unit of measure Examples: If your instrument measures in "1"s then any value between and is measured as "7" If your instrument measures in "2"s then any
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## This note was uploaded on 04/10/2010 for the course CHEM 123 taught by Professor Mchale during the Fall '09 term at Rice.

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Science Sweets and Shooting F09 - Expt 1: Science, Sweets,...

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