Population and sample design

The target population of a research study can be defined as the total set of identifiable elements of interest that the researcher is interested in when researching, and is usually apparent from the research problem and objectives (Hair et al., 2006:209; Cooper & Schindler, 2001:167). The sample is a subset of the population (Berndt & Petzer, 2011:33; Burns & Bush, 2010:364). Hereafter, the sampling units and elements need to be identified. The sampling elements are defined as those people from the defined target population who could provide the needed information, while the sampling units are those target population elements who are available for selection during the sampling process (Malhotra, 2009:371,372; Hair et al., 2006:310).

In order to select the sampling elements and units, different sampling methods are available. According to Burns and Bush (2010:364), the sample method indicates all the steps necessary to draw a sample. Literature distinguishes between probability and non-probability sampling methods (Zikmund & Babin, 2013:322; Burns & Bush, 2010:342). In probability sampling, each subject of the population has a known chance to be selected (Zikmund & Babin, 2013:322;

Malhotra & Peterson, 2006:328). Probability sampling methods include: simple random sampling, systematic random sampling, cluster sampling, and stratified random sampling (Zikmund & Babin, 2013:325-329; Berndt & Petzer, 2011:174;

Burns & Bush, 2006:333-342). On the other hand, in non-probability sampling the chance of selecting every subject is unknown (Zikmund & Babin, 2013:322;

Burns & Bush, 2006:332; Hair et al., 2006:65). Non-probability sampling methods include: convenience sampling, judgement sampling, referral (snowball) sampling and quota sampling (Zikmund & Babin, 2013:323,324; Burns & Bush, 2006:345,346; Hair et al., 2006:340-342). Subsequently, the sampling plan of this study is shown in Table 5.3 and detailed next.

Table 5.3: Main study sampling plan

Design elements Application to empirical study

Extent Republic of South Africa.

Target population South African marketing research firms that deliver quantitative research reports to clients.

Sampling frame A list of registered marketing research firms which offer quantitative research compiled by the researcher (42 in total) from the South African Marketing Research Association (SAMRA) Classifieds 2011.

Sampling unit Marketing research firms in South Africa which deliver quantitative research reports to clients.

Sampling method Non-probability purposive sampling.

Sampling element Client service director / manager who is involved with, or has an influence on, quantitative reporting processes within the identified marketing research firm.

Sample size 26 participants (spread across 15 marketing research firms).

Time frame (fieldwork) June 2012 (pilot study) July 2012 (main study).

Source: Adapted from Zikmund and Babin (2013:315) and Hair et al. (2006:311).

The target population was all South African marketing research firms which offer quantitative research to clients. The researcher defined the sampling frame by compiling a list of South Africa’s registered marketing research firms which offer quantitative research services as issued by SAMRA. The SAMRA classifieds / yearbook is an annual publication that lists and details all registered marketing research firm members – with no distinction between small, medium and large firms (SAMRA, 2011). Each qualifying marketing research firm that delivers quantitative research reports to clients, was identified as a sampling unit.

The sample units were then selected to include the seven biggest revenue contributors and then a few (eight) smaller revenue contributors (refer to section 2.3.2.2, Figure 2.2). The researcher aimed to have a mix of small, medium and large marketing research firms (in terms of revenue contribution) so as to achieve some level of industry representation. The researcher also aimed to select two sampling elements for each of the seven biggest revenue contributing marketing research firms so as to reduce possible bias or subjectivity (of a particular marketing research firm).

The choice of sampling elements was guided by the chosen sampling method.

According to Zikmund and Babin (2013:323), non-probability purposive (also known as judgemental sampling) samples are chosen either by researcher opinion or judgement. It implies that certain selection criteria are specified to identify sample elements that meet those specifications. The selection criteria are based on the researcher’s judgement of what will form a representative sample;

the choice is therefore purposive, and not random (McDaniel & Gates, 2006:314).

The researcher planned on interviewing 20 sampling elements.

This means each sample element is handpicked (deliberately chosen) as it is expected that they will provide meaning to and perspective on the research objective (Malhotra & Peterson, 2006:331). According to Bradley (2010:167) and Churchill and Iacobucci (2010:286), this sampling method is useful in exploratory qualitative research designs when the researcher wants ideas and insights on a particular subject matter where the chosen participant can offer perspective on the research objectives. The sampling units and elements were selected according to the following five criteria:

• Listing: The marketing research firm should be listed in the SAMRA classifieds.

• Revenue contribution: The seven marketing research firms that contribute close to two-thirds (64%) of the industry revenue should be included, namely:

Nielsen, Ipsos, TNS, Millward Brown, Ask Afrika, KLA and Bateleur (refer to section 2.3.2.2, Figure 2.2).

• Deliverables: The marketing research firm must provide clients with quantitative research reports.

• Position: The sample element must be involved with, or have an influence on, quantitative reporting processes (so as to assess the use of data visualisation and storytelling in quantitative reporting) – these include individuals in positions like client service directors or any other manager working in the client service department. It was important that the sample elements could articulate their thoughts and experiences to enhance the researcher’s understanding of the concepts. To have selected sampling elements with little insight into the concepts would have been illogical at this stage (Morse &

Field, 1985).

• Agreement: The chosen sampling element should have agreed to participate in the research study.

As illustrated in Table 5.3, a total of 15 sampling units (marketing research firms across South Africa) and 26 sampling elements (participants) were achieved, more than what the researcher aimed for. The sampling elements filled director or management positions at the marketing research firms where they worked (including Managing Directors, Associate Directors, Client Service Directors, Account Directors and Account Managers). Nonetheless, before the main study was undertaken in July 2012, the researcher conducted a pilot study with two participants in June 2012 (as specified in Table 5.3; refer to section 5.5.4.3).