Accuracy in measurement Why do we need it

Important terms to know n n n n n Random uncertainties Systematic error Precision

Random uncertainty n How do we calculate random/absolute uncertainty? We look at all the

Systematic errors n What creates a systematic error? n n They are created from

Significant figures n Where do they come from? n Precision of measurement n Rules

Consistency n What is consistency? n n How reproducible the results are. Consistency is

Absolute uncertainty n When is this found? This is the total uncertainty in any

Percent uncertainty n How is it found? n (Absolute uncertainty/measurement) x 100 n When

Percent to actual n How do you change % uncertainty back to actual uncertainty?

Graphing n What do you know about graphing? Direct proportion n Linear proportion n

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Accuracy in measurement Why do we need it?

Important terms to know n n n n n Random uncertainties Systematic error Precision Accuracy Consistency Absolute uncertainty Percent uncertainty Independent variable Dependent variable

Random uncertainty n How do we calculate random/absolute uncertainty? We look at all the numbers we know and estimate one place n What is our uncertainty? n Uncertainty is usually ½ of the last place written n But uncertainty is different depending on the device you use. n 34. 567 uncertainty is +/-. 0005 n

Systematic errors n What creates a systematic error? n n They are created from a faulty instrument or faulty use of the instrument. Examples: a thermometer that is off by 3. 4 degrees, not zeroing a balance before measuring a mass, or not reading a meniscus at eye level.

Significant figures n Where do they come from? n Precision of measurement n Rules for sig-figs Multiplication and division: no more sig figs than measurement with least number of sig figs n Addition and subtraction: line up the decimals and use the least significant final sig fig of the least precise number n

Consistency n What is consistency? n n How reproducible the results are. Consistency is usually closely related with precision. Why?

Absolute uncertainty n When is this found? This is the total uncertainty in any measurement. n Example: 3. 45 +/-. 005 n This number is used when adding or subtracting numbers. n Example: 34. 5 (+/-). 05 + 31. 2 (+/-). 05 = 65. 7(+/-). 1 n

Percent uncertainty n How is it found? n (Absolute uncertainty/measurement) x 100 n When is it used? You add % uncertainty when you multiply or divide numbers n Example: 28. 5 (+/-). 05 n n % uncertainty is (+/-). 18%

Percent to actual n How do you change % uncertainty back to actual uncertainty? n The actual number measurement multiplied by the % uncertainty will give the new actual uncertainty.

Graphing n What do you know about graphing? Direct proportion n Linear proportion n Indirectly proportional n Inverse linear relationship n Exponential n Cooling curve n Reaction rate n Reaction order graphs n