Levy Jennings Charts & Westgard Rules video, Done

1. What statistical measure is used for Levey‑Jennings (LJ) charts?

• Standard deviation is used for Levey-Jennings (LJ) charts

What formula due we use to get the ranges for

±1 SD

±2 SD

±3 SD

To get range just use:

mean ± (SD calculated)*(what range we are in)=

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1. What is systematic error, and what two patterns can it create in QC data?

2. What causes a trend?

3. What causes a shift?

Systematic = built into the system.
It’s an error that comes from something inside the testing process (machine, reagents, calibration, QC material, etc.) and it causes results to be consistently and predictably wrong in one direction.

• systematic error can be shift or a trend

Cause of Trend

• Trending happens when something slowly goes bad — light, tubing, electrodes, reagents, QC, temperature, filters, or calibration.

Cause of shifts:

• Shifts happen when something changes suddenly — new reagent, new calibration, sudden temperature change, or a sudden failure in sampling, dispensing, or optics.

1. How do random errors behave on a QC chart?

2. What makes random error different from systematic error?

Random error = unpredictable scatter that doesn’t follow a pattern.

1. They show unpredictable scatter with no pattern.)

2. Random error has no pattern; systematic error is predictable and directional.

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