Accuracy and Precision

Qualitative Measurements Qualitative measurements give results that are descriptive and non-numerical. Example: Colors, smells

Quantitative Measurements Quantitative measurements give results that are definite, usually as numbers and units. Example: 27mL

Accuracy and Precision Measurements work best when they are accurate and precise

Accuracy Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured. To evaluate the accuracy of a measurement, it must be compared to the correct value.

Precision Precision is a measure of how close a series of measurements are to one another. The precision of a measurement depends on more than one measurement.

Accuracy and Precision Reproducibility Check by repeating measurements (Trials) Poor precision results from poor technique Correctness Check by using different methods Poor accuracy results from procedural or equipment flaws

Accuracy and Precision

Accuracy and Precision In this picture, all of the darts land on the bulls-eye which illustrates good precision and accuracy. In this picture, all of the darts land near each other, but away from the bulls-eye which illustrates good precision, but poor accuracy.

Accuracy and Precision Here the darts are not close to each other, but are close to the bulls-eye indicating poor precision, but good accuracy. Finally, the darts are not close to each other or near the bulls-eye indicating both poor accuracy and poor precision.

Accuracy and Precision What is the following an example of: You did an experiment to see at what degree water boiled in Celsius. You got the following results. T1- 65 T2- 67 T3 – 66 Accuracy or Precision???? 99.98 C

Accuracy and Precision A basketball player throws 100 free-throws; 95 of these balls go through the goal; 5 miss the goal entirely. Describe the precision and accuracy of the free-throws. Both

Accuracy and Precision The same player is having an off day; 5 balls go through the goal; the other 95 balls bounce off of the rim. Describe the precision and accuracy of the throws. Precise, but not accurate

Accuracy and Precision Each of five students used the same ruler to measure the length of the same pencil. The results are as follows: 15.33 cm, 15.34 cm, 15.33 cm, 15.33 cm, 15.34 cm. The actual length of the pencil was 15.85 cm. Describe whether accuracy and precision are each good or poor for these measurements.

Draw a target diagram that shows precision but not accuracy .

Draw a target diagram that shows accuracy but not precision

Draw a target diagram that shows both accuracy and precision

Practice a)78.1 mL, 43.9 mL, 2 mL (should be 100mL) Precise, Accurate, Both, Neither b) 68.1 mL, 68.2 mL, 68.0 mL (should be 68.1mL) c) 98.0 mL, 98.2 mL, 97.9 mL (should be 100mL) d) 72.0 mL, 60.3 mL, 68.1 mL (should be 100mL)