Math: Accuracy & Precision

Divide that number (0.2 cm) by 2

0.1 cm. This is the approximate + range from the average.

Precision Problems: A group of students worked in separate teams to measure the length of an object, Their data: 2.65, 2.75, 2.80, 2.77, 2.60, 2.65, 2.68. Subtract the highest value from the lowest value.

0.2 cm. This is the range or spread.

The precision of the measurement can be shown as average + range. The precision of the measurement is what?

2.7 + 0.1 cm.

Precision Problems: A group of students worked in separate teams to measure the length of an object, Their data: 2.65, 2.75, 2.80, 2.77, 2.60, 2.65, 2.68. The average length is what?

2.7 cm. This is the mean or average.

Expressing Errors in Measurement: A student took a calibrated 200.0 gram mass weighted it on a laboratory balance, and found it read 196.5 g. What was the student's percent error?

200-196.5 ------------ x 100 = 1.75% 200

Expressing Errors in Measurement: A student measured the specific heat of water to be 4.29 J/g Celsius. The literature value of the specific heat of what is 4.18 J/g Celsius. What was the student's percent error?

4.18-4.29 ---------- x 100 = 2.63% 4.18

Precision versus Accuracy: 5 dots in the exact measurement (the middle)

Both accurate and precise

Definition: Precision

How close a measurement is to every measurement

Definition: Accuracy

How close measurement is to the exact measurement

Precision versus Accuracy: 5 dots scattered through out the whole board

Neither accurate nor precise

Precision versus Accuracy: 5 dots in the last layer, farthest from the exact measurement

Precise, but not accurate