NZQA Expiring unit standard
8962 version 6
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Title
Evaluate sampling methods used within the New Zealand dairy
industry
Level
4
Credits
6
Purpose
People credited with this unit standard are be able to: explain
the use of random sampling and factors which limit its practical
use; calculate the mean and standard deviation and the
proportion of data likely to lie within 1, 2 standard deviations of
the mean; identify the difference between attribute and variable
sampling, and use an attribute sampling plan; define sampling
vocabulary and terms used in Codex sampling procedures;
identify methods used in the New Zealand dairy industry to
reduce the cost of true random sampling; plot data on Control
and Cumalative Sum (CUSUM) charts; estimate the chance of
rejection of a lot using an Operating Characteristic curve (OC
curve); and determine the number of samples needed for
problem solving investigations where a single defect in the
sample denotes a problem.
Classification
Dairy Manufacturing > Dairy Laboratory Methodology
Available grade
Achieved
Entry information
Critical health and
safety prerequisites
Open.
Explanatory notes
1
Reference documents
Codex General Guidelines on Sampling (codex alimentarius commission FAO/WHO
of the United Nations, CAC/GL 50, 2004) available from
http://www.codexalimentarius.net.
2
Definitions
Organisational Requirements refers to instructions to staff on policy and procedures
which are documented in memo or manual format and are available in the workplace.
These requirements include but are not limited to – site specific requirements,
company quality management requirements, approved codes of practice and
guidelines, and legislative requirements.
Legislative requirements in this unit standard refer to legislation and regulations that
include but are not limited to – Animal Products Act 1999, Animal Products (Dairy)
Regulations 2005, relevant Dairy Specifications/Notices.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
3
8962 version 6
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Data for calculations will be provided by the assessor.
Outcomes and evidence requirements
Outcome 1
Explain the use of random sampling and factors which limit its practical use.
Evidence requirements
1.1
Random sampling is defined according to Codex General Guidelines on
Sampling.
1.2
Explanation identifies the two main reasons why random sampling is favoured.
Range
international respectability, fairness (unbiased estimates of
population parameters).
1.3
Two situations in the dairy industry are identified, and reasons are given, in
which true random sampling may be impracticable.
1.4
A situation in the dairy industry is identified in which a sampling method
apparently equivalent to the random sampling method may give a false result,
and an explanation is provided as to the source of bias in the method.
1.5
A random sample is produced from a defined population with an explanation of
the method used.
Outcome 2
Calculate the mean and standard deviation and the proportion of data likely to lie within 12 standard deviations of the mean.
Evidence requirements
2.1
The mean and standard deviation (n-1) are calculated from a given set of
positive data.
2.2
The proportions of data likely to lie within the limits of 1 standard deviation from
the mean, and 2 standard deviations from the mean, are stated for normal
distribution.
Range
a normal distribution with mean at least three times the standard
deviation.
Outcome 3
Identify the difference between attribute and variable sampling, and use an attribute
sampling plan.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
8962 version 6
Page 3 of 5
Evidence requirements
3.1
A given set of data is identified as containing variable or attribute data.
3.2
A given set of E. coli results is identified as containing variable or attribute data.
Range
19 out of 20 E. coli results are given as negative.
3.3
A sample lot is determined as acceptable or rejectable from a given attribute
sampling plan, sample size, acceptable quality level (AQL) of plan, and number
of defectives.
3.4
A given set of data is assigned a quality grade in accordance with the product
specification.
3.5
The producer’s risk is stated for a given consumer’s risk.
Outcome 4
Define sampling vocabulary and terms used in Codex sampling procedures.
Evidence requirements
4.1
Sampling vocabulary and terms are defined in accordance with Codex General
Guidelines on Sampling.
Range
AQL, Acceptance Number, Consumer Risk (CR), Inspection Level,
Lot, Lot Size, Operating Characteristic Curve (OC curve),
Probability of Acceptance, Producer’s Risk (PR), Rejectable
Quality Level (RQL), Sampling Plan.
Outcome 5
Identify methods used in the New Zealand dairy industry to reduce the cost of true random
sampling.
Evidence requirements
5.1
Methods used to reduce the cost of true random sampling are explained in
accordance with Codex General Guidelines on Sampling and legislative and
organisational requirements.
Range
quasi-random sampling, composite sampling, continuous
sampling.
5.2
An example of where each method is used to reduce the cost of true individual
random sampling in the dairy industry is given along with a possible
disadvantage of each.
Range
quasi-random sampling, composite sampling, continuous
sampling.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
8962 version 6
Page 4 of 5
Outcome 6
Plot data on Control and CUSUM charts.
Evidence requirements
6.1
Additional data given are plotted on given Control and CUSUM charts of the
same data.
Range
6.2
data provided are generally within upper and lower limits of control
chart, data provided contains a single change of mean.
The point is identified at which a change in mean occurs.
Outcome 7
Estimate the chance of rejection of a lot using an OC curve.
Evidence requirements
7.1
The chance of rejection of a lot with x% defective is estimated from a given OC
curve.
7.2
The proportion of defectives corresponding to a y% probability of rejection is
estimated from a given OC curve.
Outcome 8
Determine the number of samples needed for problem solving investigations where a
single defect in the sample denotes a problem.
Evidence requirements
8.1
From a given formula, the number of samples is determined that must be taken
to give at least a x% chance of finding at least one defective if there are y%
defectives in the population.
Range
given formula is N ≥ [log(1-c)/log(1-d)] (where N is the number of
samples required, c is the confidence required, d is the proportion
of defects in the population which it is necessary to pick up).
This unit standard is expiring. Assessment against the standard must take place by
the last date for assessment set out below.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
8962 version 6
Page 5 of 5
Status information and last date for assessment for superseded versions
Process
Version Date
Last Date for Assessment
Registration
1
28 April 1997
31 December 2017
Revision
2
2 July 1999
31 December 2017
Revision
3
13 June 2003
31 December 2017
Rollover and
Revision
4
25 September 2006
31 December 2017
Rollover and
Revision
5
17 July 2009
31 December 2017
Review
6
15 October 2015
31 December 2017
Consent and Moderation Requirements (CMR) reference
0022
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA,
before they can report credits from assessment against unit standards or deliver courses
of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by
NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and
which are assessing against unit standards must engage with the moderation system that
applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies
to this standard are outlined in the Consent and Moderation Requirements (CMR). The
CMR also includes useful information about special requirements for organisations wishing
to develop education and training programmes, such as minimum qualifications for tutors
and assessors, and special resource requirements.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016