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5. Characterization of the data distribution

•

Build the histogram of the data:

Bi-modal

Truncated

Asymetric



Examples of data distributions

Normal



Understand the shape of your data distribution. Was it expected?

•

Studied case: normal distribution



Why?

✓

Most of radiotherapy processes follow a normal distribution.

•

Important comment: with certain precautions*, it remains

possible to use SPC tools for non normal distributions

Part 1

Introduction to

SPC

Part 2

Essential

concepts to

start with SPC

Part 4

Conclusion

Part 3

SPC in

practice

NALYZE

✓

SPC’s traditional formulas:

based on the hypothesis of a

normal distribution.

(* no more link between limits of control charts and the



risk, no

more link between capability and % of data out of specifications)

03/10/17