The Weights and Measures (Packaged Goods) Regulations 2006

4.  CHECKING OF AVERAGE ACTUAL VOLUME OF THE CONTENTS OF THE INDIVIDUAL PACKAGES MAKING UP A BATCH

4.1 A batch of packages shall be considered acceptable for the purpose of this check if the mean value

of the actual quantity of the contents of the packages in the sample is greater than the value:

4.2 In this formula:

Q_n

=

the nominal quantity of the package,

n

=

the number of packages in the sample for this check,

s

=

the estimated standard deviation of the actual contents of the batch,

^t₍₁₋α₎

=

0.995 confidence level of a Student distribution with δ = n−1 degree of freedom

4.3 if χ_i is the measured value for the actual contents of the i-th item in a sample containing n items, then:

• The mean of the measured values for the sample is obtained by the following calculation:

  

4.4 and the estimated value of the standard deviation s is obtained by the following calculation:

• the sum of the squares of the measured values:

  

• the square of the sum of the measured values:

  

• then

  

• the corrected sum

  

• the estimated variance:

  

• the estimated value of the standard deviation is:

  

Criteria for acceptance or rejection of the batch of packages for checking the mean

4.5 Criteria for non-destructive testing:

		Criteria
Number in batch	Number in sample	Acceptance	Rejection
100 to 500 (inclusive)	30	≥ Qn — 0.503s	< Qn — 0.503s
> 500	50	≥ Qn — 0.379s	< Qn — 0.379s

4.6 Criteria for destructive testing:

		Criteria
Number in batch	Number in sample	Acceptance	Rejection
Whatever the number (≥ 100)	20	≥ Qn — 0.640s	< Qn — 0.640s

4.7 For batches of fewer than 100 packages, the average of the measured values of the actual contents shall be determined by application of the formula in paragraph 4.3 where n equals the number of packages in the batch. If the average is equal to or greater than the nominal quantity of the packages in the batch, the batch shall be considered as acceptable for the purposes of the check.