DAY 13 — Type A & Type B Evaluation

What are Type A and Type B evaluations?

Two approaches for evaluating components of measurement uncertainty

What is Type A evaluation based on?

Statistical analysis of measured values

What is Type B evaluation based on?

Other available information

Is Type A automatically better than Type B?

No

What determines whether an evaluation is Type A or Type B?

How the uncertainty component is evaluated rather than simply where the information came from

What is the most important rule about Type A and Type B?

The source does not determine the type

Can a calibration certificate result in Type B evaluation?

Yes

Can repeatability data be Type A?

Yes

What is an example of Type A evaluation?

Statistical analysis of repeated measurement data

What does Type A use?

Real measured data and statistical analysis

What is Type A evaluation according to VIM3?

Evaluation of a component of measurement uncertainty by statistical analysis of measured quantity values obtained under defined conditions

What are repeated measurements used for in Type A?

They provide experimental data for statistical evaluation

What are the basic steps for repeated measurements?

Calculate the mean find the standard deviation and calculate the standard uncertainty

What is the Type A formula?

uA = s divided by the square root of n

What does s represent?

Experimental standard deviation

What does n represent?

Number of observations

What does ν represent?

Degrees of freedom

What is the difference between s and s divided by square root of n?

s describes the dispersion of individual observations while s divided by square root of n is the standard uncertainty of the mean

Should s automatically be used as the uncertainty of the mean?

No

Is Type A limited only to simple repeated observations?

No

What is Type B evaluation?

Evaluation of a component of measurement uncertainty using information other than a Type A statistical analysis

What information can support Type B evaluation?

Calibration certificates manufacturer specifications previous measurement data reference data experience scientific knowledge and drift information

Does a calibration certificate automatically determine the evaluation type?

No

What should be checked when using a calibration certificate for Type B?

The stated distribution coverage factor and validity of the information

What example Type B calculation is shown?

If certificate uncertainty is approximately normal and k=2 then u equals 0.20 divided by 2 which is 0.10 °C

What is the common distribution formula for a normal distribution when coverage factor k is given?

u = a divided by k

What is the standard uncertainty for a rectangular distribution?

u = a divided by the square root of 3

What is the standard uncertainty for a triangular distribution?

u = a divided by the square root of 6

Should a distribution be selected simply for convenience?

No

Can an uncertainty budget contain both Type A and Type B components?

Yes

What is an example of a Type A contributor in the infographic?

Repeatability

What is an example of a Type B contributor?

Reference standard certificate

What is another Type B contributor?

Resolution

Can environmental variation be Type A or Type B?

Yes

What do Type A and Type B evaluations both produce?

A standard uncertainty

What is the uncertainty-budget process shown?

Identify contributors estimate input values and uncertainties assign probability distributions determine standard uncertainties apply sensitivity coefficients check correlation and combine to obtain combined uncertainty

What are sensitivity coefficients used for?

To determine how input quantities affect the measurement result

What is checked before combining uncertainty contributions?

Whether relevant inputs are correlated

What is a Type B red flag?

Saying that Type B is less accurate

Why is saying Type B is less accurate incorrect?

Type B is simply a different evaluation approach

Is repeatability automatically Type A?

Not necessarily

the type depends on how the component is evaluated

Does a certificate uncertainty automatically equal standard uncertainty?

No

Should a rectangular distribution always be used for every Type B component?

No

What is the calibrator's mindset?

Do not ask only where the uncertainty came from

ask how it was evaluated

What does the phrase "The method matters" mean?

The evaluation method determines whether a component is Type A or Type B

What is the main lesson of Day 13?

Type A and Type B are different evaluation approaches and both can produce valid standard uncertainty components