With linear backgrounds, a background slope may be determined and either background measurement used to calculate the value under the peak. BG 1 lies beneath an interfering peak. Non-linear backgrounds are also a potential problem in determining background. Accuracy is affected if the compositions of the standards are not well known whereas precision is not. With these materials, one only has to look for impurities and make sure that they are insignificant, not determine their abundances.
Precision refers to how well a given measurement or results can be reproduced.
Values can be very precisely determined and still be very inaccurate. Conversely, a number of imprecise analyses may average to a very accurate value. Precision is effectively limited by counting statistics when dealing with X-ray analysis. Many factors, many out of the control of the analyst, can affect both precision and accuracy. Focus problems, which can produce significant unsystematic errors and a loss of precision and accuracy.