Bias *affects all measurements the same way, making them all too large or too small*. Bias is detected by comparing to an external standard.
## Chance error
Chance errors *change from measurement to measurement but average out over time*. There is no way to remove all chance errors from a measuring process. An example of chance error would be starting a stopwatch then attempting to stop it at exactly 5 seconds, then repeating. The times will vary, but each measurement will vary in a different way.
