## How is bias calculated?

Calculate bias by finding the difference between an estimate and the actual value. Dividing by the number of estimates gives the bias of the method. In statistics, there may be many estimates to find a single value. Bias is the difference between the mean of these estimates and the actual value.

## What is r4s rule?

R4s indicates a rejection when one control measurement in a run exceeds a +2s control limit and another exceeds a -2s control limit. This “range” rule is sensitive to changes in the width of the distribution, therefore it is a good indicate of increases in random error or changes in the precision of the method.

**How many Westgard rules are there?**

5 different control rules

### What is LJ chart?

A Leveyâ€“Jennings chart is a graph that quality control data is plotted on to give a visual indication whether a laboratory test is working well. The distance from the mean is measured in standard deviations.

### What are the control limits of the Levey Jennings chart?

In many laboratories, this rule is used to reject a run when a single control measurement exceeds a 2s control limit. 13s corresponds to a Levey-Jennings chart having control limits set as the mean plus/minus 3s. An analytical run is rejected when a single control measurement exceeds a 3s control limit.

**What is calibration and control?**

Calibration is the process of testing and adjusting the instrument or test system readout to establish a correlation between the instrument’s measurement of the substance being tested and the actual concentration of the substance.