Selection of interviewees

Sampling procedure and sampling frame

Sampling is the process of choosing samples from which data is collected that is potentially relevant to the research being conducted (Aldridge and Levine 2001).

Sample selection is vitally important, considering cost, time, feasibility and quality (Lynn 2002). The ultimate purpose of survey sampling is to select a set of members from a population so that a description of those members accurately describes the whole population from which they are drawn (Vaus 1996). There are two kinds of sampling:

probability sampling (or random) and non-probability sampling (Remenyi et al. 1998).

Which way to choose depends on the researcher‘s aim. Some researchers select samples to provide the maximum theoretical understanding, while others are concerned about a sample to represent the whole population (Arber 1993). In quantitative research, the sample should be representative of the population from which it is drawn (Oppenheim 1992). Probability sampling provides a method to meet this criterion. Random selection

enables researchers to access a body of probability theory that provides the basis for the estimates of population parameters and estimates of error (Gall et al. 2003).

The researcher tried to make the samples sufficiently accurate, free from omissions and duplications and up to date, as advised by Saunders et al. (2009). In order to ensure that the selected samples were as representative as possible, the researcher adopted a disproportionate stratified random sampling technique¹, which gives a greater degree of representation and decreases the probable sampling error that would occur with a simple random sample of the same size (Vaus 1996).

Specifically, the sampling frame of port stakeholders was categorised into five groups based on Murphy et al. (1992), Murphy and Daley (1994) and Notteboom and Winkelmans (2001) who identify and categorise port stakeholders into shippers, forwarders, shipping lines and port managers. Bichou and Gray (2004) find that shipping lines, freight forwarders, shippers, inland transport providers and port operators are the important port customers/suppliers. They also note that ports have diversified clients and no client holds a dominant role.

The current researcher prefers to use the term consignors/consignees rather than shippers, to refer to local port related manufacturing industries, retailers and distributors, because apart from shippers, receivers (consignees) are also important port customers.

Transport operators (railways, truckers), port labour and stevedores, warehousing providers and vessel/cargo agencies/forwarders are referred to as port service providers.

Port managers refer to port authorities and port operators. Local environmental groups, local residents, local/regional and national government and government agencies, academic professionals, consultants are considered as one group of port stakeholders - other port stakeholders. Hence, in this research, port stakeholders are categorised into five groups: consignors/consignees, PSPs, carriers, port managers and other port stakeholders.

The aim in selecting these broad categories of questionnaire respondents was to cover port stakeholders as comprehensively as possible. Certain samples were randomly selected from each of these groups, not by equal number but in different proportions as their sample sizes vary from port to port. With this technique, the target groups that

1 Stratified random sampling is a procedure which first categorises a population into subgroups and then randomly selects from each subgroup until a desired number is reached, either proportionately or disproportionately, from each subgroup- www.setda.org/web/guest/glossary.

were closely related to ports were identified on the basis of literature review, previous surveys, interviews and networking with professional and trade bodies. The reason for collecting data from various groups is that each group of port stakeholders has a distinct interest and role in the global logistics pipeline (Murphy and Daley 1994).

Selection of interview interviewees

Sample selection refers to a more general process of focusing on a portion of the population. Eisenhardt (1989) claims that a key approach to limit the bias of interviewees is using numerous and highly knowledgeable interviewees who view the focal phenomena from diverse perspectives. Good interviewees are those who not only have knowledge and experience the researcher requires but also are able to reflect, have the time to participate, and are willing to participate (Morse 1994). The quality of port interviewees is crucial for the quality of the outcomes of the interviews in the empirical research. That is why the interviewees were carefully selected to avoid bias.

Empirical research which attempts to improve strategy is likely to benefit from the involvement of managers who actually participate in their organisations‘ strategy formulation. This implies that an appropriate methodology should be based on groups of managers who have the experience and expertise to understand the products and services of their organisations (Slack 1994).

As qualitative research does not aim to draw statistical inference, purposive sampling is often employed in the investigation (Sekaran and Bougie 2010). In this research, the interviewees were purposively selected on the basis of in-depth knowledge and expertise of performance in the port. Three criteria were used for interviewee selection:

job position, working experience in the port sector and involvement in port management.

Experts in various high positions from five key port stakeholders were interviewed, which is a very important way to validate the findings. This means that qualitative data from interviews for this research was collected using a key interviewee approach. The technique of snowball sampling was also employed to help with the selection of appropriate interviewees.

As this research was conducted on the basis of mixed methods, the large number of interviewees that are needed in quantitative research was not a central issue for the qualitative research (Malhotra and Birks 2003). The number of interviews depends on when the researcher feels he/she has reached a point of theoretical saturation or stability (Sekaran and Bougie 2010), and no new information or major points emerge from the

interviews (Patton 2002). Perry (1998) indicates that 35-50 is the appropriate number of interviews for a doctoral research. Based on the above arguments, forty interviews in Phase 1 from January to March of 2009 were conducted (Section 4.3.4). The detailed profile of interviewees is given in Table 4.6.

Table 4. 6 Profile of interview participants

As discussed for the selection of interview interviewees, the selection of questionnaire respondents should also apply the same criteria: experts from various port stakeholders to provide invaluable data and avoid respondents bias, also using a key interviewee approach. Therefore, the questionnaire surveys were sent to top management of five groups of port stakeholders.

For the number of questionnaire respondents, Sekaran and Bougie (2010) propose that sample sizes of 30-500 are appropriate for most research. The sample size can be flexible, given the uncertainties (e.g. resources, time, and funds limitation) of the proposed research under specific situations. For this research, the questionnaire sample size was decided by referring to the table provided by Sekaran (1970; 2000) that offers general scientific guidelines for sample size decisions. The number of the main port stakeholders in the Humber was estimated to be around 400 and that in Xiamen was estimated to be around 1300. According to Sekaran and Bougie (2010), when the population size is 400, the sample size should be 196; when the population size is 1300, the sample size should be 297. Therefore, 200 questionnaires in the Humber and 300 questionnaires in Xiamen were distributed.

A random sampling frame of 500 companies was then selected to reflect the shares of five different types of organisations involved in port activities. Then 500 specialists who had rich experience with ports and who knew ports well (one from each company) were drawn from the ―population‖. The numbers of respondents in the five sample categories were not equal because the ―populations‖ were not equal. As port stakeholders are not defined clearly and in detail, and the numbers of port stakeholders were not available in the public statistics, the researcher had to estimate the number of main port stakeholders who would be representative of the ports in the two regions, based on the interviews with port managers.

As indicated earlier, the questionnaire survey was conducted in the Humber estuary (UK) and Xiamen (China) from May to July of 2009. In the UK, the first company list was obtained from the port authority when interviews were conducted with ABP, the regional port authority, port owner and sometimes a port operator as well. The ABP handbook provides a list of the regional port stakeholders such as port users and port service providers. The second list was obtained from the Chamber of Commerce, which includes the regional importers and exporters that are port end users. Then some association members such as members in NETTA (North East Timber Trading Association), Team Humber Marine Alliance, Yorkshire Forward (the Regional Development Agency), Humber World Trade Centre, the local City Councils, UK Trade and Industry, BIFA-British International Freight Association, RHA (Road Haulage Association) and British Services (Hull Shipping Services) were contacted to try to find appropriate respondents. The lists provided the sampling frame which represents all the elements in the population from which the sample is drawn (Sekaran and Bougie 2010).

200 companies were selected from these lists by means of stratified random sampling.

In Xiamen, the Xiamen Logistics Association and Xiamen Industrial and Commercial Administrative Bureau provided the researcher with company lists, which included all organisations involved in Xiamen ports and logistics. The list of Xiamen University Alumni also helped the researcher to select some interviewees who were working for the ports or port related companies. Based on these lists, the researcher selected 300 companies by stratified sampling techniques. Table 4.7 shows the company profile for questionnaire distribution. Xiamen 162 valid responses (valid response rate=54%) were received. This response rate was satisfactory as the usual questionnaire survey response rate in logistics and supply chain management is between 10-30%. Aryee‘s (2005) PhD thesis on supply

chain integration performance had a response rate of 12%; Adeleye‘s (2002) PhD thesis on manufacturing agility had a response rate of 18.3%, Hoek‘s (2001) journal paper on the contribution of performance measurement to the expansion of third party logistics alliances in the supply chain had a response rate of 27%, Gordon and Sohal‘s (2001) research on assessing manufacturing plant competitiveness had a response rate of 26%.

Lirn‘s (2004) research on port selection had a very high response rate of 90% from global carriers, but its sample frame was small (only 20). Murphy et al. (1991) achieved a response rate of 21.1% with an effective sample size of 383 (industrial companies in the US) and 81 useable responses for their survey on international water transportation.

It should be acknowledged that the results represent the knowledge and interpretations of individuals from the different port stakeholders rather than their company views, although this research has tried to select the respondents to be as representative as possible of their companies. Interviewees for both interviews and questionnaires were considered adequately qualified to answer the questions from the questionnaires and interviews. This approach was considered appropriate for the population and was considered adequate to produce reliable and valid data.