Thursday, November 11, 2010

Review packet #13

Q: Explain the difference between precision and accuracy. Suppose you make three different mass measurements of a sugar sample you knew to have a mass of 1 gram. How would you know whether or not the measurements were accurate? How would you know whether or not they were precise? Could the three measurements be precise, but not accurate? Explain.

A: Accuracy is how close a measurement comes to the true value of something; or correctness Precision is how close a series of measurements are to each other. If you knew the mass of sugar was 1 gram and got values of 1,1.02, and .96, these measurements would be accurate but not precise. They are accurate because they are close to 1, however they are not as close to each other. Lets say you get values of 2, 2.01, and 2.01. These values would be precise because they are so close to each other, but not correct or accurate. The values are precise if they are all close to each other. The values are accurate if they are all close to the known CORRECT value: 

Here is a picture to help: