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CHAPTER 7 SAMPLING
7.3 After the items to be priced have been selected, detailed specifications are prepared to ensure that all staff involved in price collection and compiling the CPI have exactly the same understanding of which particular items are to be priced. For most goods, it is a straightforward matter of describing their characteristics. These may include brand name, material of composition, model number, style, size, and type of packaging.
7.4 It is generally more difficult to specify service items adequately because both quantity and quality are harder to describe. In addition, more detailed descriptions are usually required in the specifications for services in comparison to those for goods. For example, the specification for a can of tomato soup may consist of only two characteristics: the brand name, and the weight of the can. However, the specification for a travel service such as a bus fare would have three characteristics: the concessional status of the traveller (e.g. adult, student, child, pensioner); the specific bus route including the origin of the journey and its destination; and the time of the journey (e.g. peak or off-peak).
7.5 The preferred practice in pricing goods for the CPI is to price identical specifications (i.e. the same brand name, size or model of product) at all outlets in all capital cities. The nature of many goods and services, however, often makes this impossible. In practice, products fall into one of two categories.
(i) National standard. These products are available in all capital cities, and at the vast majority of respondent outlets. They can be readily and clearly defined by characteristics such as make, model, and size as a specification for use nationally. ABS field officers have no latitude in choosing the product for pricing. Examples include motor vehicles, and the major brands of breakfast cereals.
(ii) Respondent standard. These products can be readily defined by form and function, but a multitude of brands and models may exist making it impossible to guarantee that any one example of the product will be available Australia wide. A generic description is provided in sufficient detail to ensure that the field officers will be able to locate an example of the product. This example must be consistent with the quality of those chosen in other outlets within the same city, and broadly consistent with those in other cities. An example of the required type of product is chosen at each respondent outlet, and its defining characteristics are added to the generic description for future use at that respondent. Examples of these products are beer, daily newspapers, and furniture.
SELECTING THE SAMPLE OF OUTLETS FOR PRICING
7.6 Consumers purchase the goods and services priced in the CPI from a wide variety of retail outlets. Examples of these outlets include supermarkets, department stores, hotels, motor vehicle dealerships, doctors’ surgeries, electricity and gas shopfronts, travel agencies, schools, and child care centres. For every item selected for pricing, the main types of outlets from which the CPI population group buys the items need to be identified so that the ABS can select representative samples of these outlets.
7.7 In selecting outlets for inclusion in samples for the CPI, the following factors are taken into account.
CHANGES TO OUTLET SAMPLES
7.8 The samples of respondents are reviewed regularly to ensure that they remain representative of the CPI population group's sources for purchases. Events such as company takeovers, new retailers entering the market, existing chain organisations opening new outlets, or new shopping complexes opening up can all lead to the need to change the samples of respondents so that they continue to be representative of the CPI population group's purchases. Changes to the sample of respondents or specifications are carried out using the splicing process discussed in Chapter 4.
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