Accuracy Versus Precision Practice

The table below shows sets of measurements made by four different thermometers. The thermometers each took four measurements of the temperature of a beaker of boiling water. The theoretical (accepted) value for the temperature of boiling water is 100 degrees Celsius. The average of the values measured by each thermometer is given in the table and the range of measured values (largest value - smallest value) is also given for each thermometer.

The data taken by Thermometer 1 is accurate because the average value of the measurements made by Thermometer 1 is equal to the known value of the boiling point of water. (We know this because the average of the measurements taken by Thermometer 1 is the same as the accepted value for the boiling point of water.) The set of measurements made by Thermometer 1 is also precise because the measurements made by Thermometer 1 are all close to the same value. (This is indicated by the small range.)

The data taken by Thermometer 2 is accurate (average is close to 100 degrees Celsius) but not precise (large range). The data taken by Thermometer 3 is not accurate (average is not close to 100 degrees Celsius), but it is precise (small range). The data taken by Thermometer 4 is neither accurate nor precise.

The data taken by Thermometer 1 is accurate because the average value of the measurements made by Thermometer 1 is equal to the known value of the boiling point of water. (We know this because the average of the measurements taken by Thermometer 1 is the same as the accepted value for the boiling point of water.) The set of measurements made by Thermometer 1 is also precise because the measurements made by Thermometer 1 are all close to the same value. (This is indicated by the small range.)

The data taken by Thermometer 2 is accurate (average is close to 100 degrees Celsius) but not precise (large range). The data taken by Thermometer 3 is not accurate (average is not close to 100 degrees Celsius), but it is precise (small range). The data taken by Thermometer 4 is neither accurate nor precise.