1. Scientific Methods Error Analysis Random and Systematic Errors Precision and Accuracy

2. Errors What is an error? An error has occurred if the is a difference b/w experimental and correct (perfect) values Random errors Caused by physical changes e.g. temp; imperfections in observation; readability of instruments Systematic errors zero error, calibration errors, repeated imperfections in readings

3. Accuracy and Precision An accurate experiment the smaller the systematic error in an experiment or reading, the more accurate it is. Repeating the experiment several time does not increase its accuracy! A precise experiment A experiment is more precise if it has a small random error. Repeating an experiment increases its precision

4. Accuracy and Precision value measured value true value measured value true value (a) Accurate but low precision (b) Less accurate, more precise

5. Errors on Graph Graphs can bring out the presence of a random or systematic error Perfect graph plotted points, all lie on a straight line, which passes through the origin. Random error graph plotted points are scattered over the surface Systematic error graph Straight line parallel to that of perfect line, but y-shifted

6. Errors on graph perfect results random error systematic error Quantity A Quantity B

7. Uncertainty Consider the reading for the volume of a liquid as measured with a measuring cylinder What is the reading? How sure are we that it is not

8. Uncertainty