Research approaches ··································································

The research approach is the particular direction of the research design derived from the research philosophy. Creswell (2007) identified three approaches; quantitative, qualitative and mixed methods.

The quantitative approach investigates the observable phenomena via statistical, mathematical or computational techniques. It is one of the most common approaches to conduct social research because it is widely accepted that the quantifiable result can support opinions and concepts. The qualitative approach gathers in-depth information about human behaviour and various aspects of social life. It uses words rather than numbers to describe people and research phenomena in natural situations (Amaratunga et al., 2002). Each approach uses specific research techniques e.g. survey for quantitative research, content analysis for qualitative research. The mixed methods approach recognises that quantitative and qualitative approaches both have limitations, and when both are implemented in the same piece of research, one supplements the shortcomings of the other. Table 6.2 shows the differences of the three approaches.

Table 6.2 Quantitative, qualitative and mixed methods approach

Quantitative approach Qualitative approach Mixed methods approach

• Generally associated with Positivism

• Involves collecting and converting data into numerical form

• Data collection follows a strict procedure and preparation for statistical analyse • Based on a representative sample of the wider population/group to collect data • Objective • Generally associated with Interpretivism • Involves obtaining rich

and complex personal experience which cannot be gained from large groups • Involves a smaller number of participants • More subjective • Incorporates both qualitative and quantitative approaches • Use appropriate data

collection and analysis methods depending on the nature of the question • Has the advantages of

triangulation

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Quantitative research focuses and relies on measurement and calculation, and qualitative research focuses on the description of the meaning, features and symbols of study subjects, moreover, quantitative approach is more structured, and the qualitative approach is less structured (Feng, 2013). Therefore, most researchers use both in a complementary way to improve the research quality. Ragin (1994) explained that ‘most quantitative data techniques are data condensers. They condense data in order to see the big picture. Qualitative methods, by contrast, are best understood as data enhancers. When data are enhanced, it is possible to see key aspects of cases more clearly’. Patton (2002) stated that the quantitative methods require the use of standardised measures for many responses, and qualitative methods can facilitate the study in depth and detail. The varying perspectives and experiences from the qualitative inquiry can fit into a limited number of predetermined responses. Both quantitative and qualitative research have their strengths and weaknesses (Table 6.3).

Table 6.3 Strengths and limitations of two approaches

Strengths Limitations

Quantitative Research Methods

• Provide wide ranging information

• Collect data fast and economically

• Use statistical techniques to aggregate large amounts of data which can help the decision- making

• Tends to be inflexible and artificial

• Not very effective in

understanding processes and peoples’ thoughts

• Not helpful in developing theories

• Not best suited for decision- making about future changes

Qualitative Research Methods

• More natural approach to data collection

• Offers guidance on processes, and provides information for adjusting the issues

• Provides an understanding of people’s attitudes and real meanings

• Makes contribution on theory generation

• Take long time and large resources to collect data • Difficult to analyse and

interpret data

• Low credibility to decision- makers

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The primary consideration of research method selection is to answer the questions raised by the research. To meet the needs of the research, many researchers combine quantitative and qualitative methods to gain a full understand of complex problems (Hyland, 2016). Mixed methods approach involves collecting and analysing data through integrating quantitative and qualitative approaches. This approach provides both breadth and a better understanding of the research question (Creswell, 2014), the greatest advantage of this approach is the possibility of triangulation by using several methods, data sources and researchers to examine a single problem (Bazeley, 2004). The case for a combined research approach in evaluations or assessment has been convincingly demonstrated, for example, the World Bank used a mixed approach for developing poverty assessments in 1990 (Garbarino and Holland, 2009).

This research combined quantitative and qualitative research to collect a wide range of data relating to the sustainability of highway infrastructure projects. A qualitative approach was first used to identify and select the preliminary indicators from existing evaluation systems or frameworks. Using the preliminary indicators system, a quantitative approach was undertaken to obtain the perceptions of professional groups on sustainability in highway infrastructure projects. The determination and weighting of indicators for the sustainability assessment model needs a large sample, and this can be achieved using a quantitative approach. The goal of the quantitative approach was to determine the relative indicators, but the results only focus on current and recent projects, therefore a qualitative approach is required to discover why and how. The final step in data collection adopts a qualitative approach to examine the opinions of experts associated with sustainable highway infrastructure projects.

According to Appleton and Booth (2005), when using the integrated research approach of combining quantitative and qualitative methods, their comparative advantages must be understood. However, this research used a quantitative approach to collect data that can be aggregated and analysed to describe the significance of the individual factors of sustainable highway infrastructure projects. The qualitative approach helped to probe and explain those indicators and their relationships. It was possible to interpret observed patterns and trends, and to analyse the different understanding of the dynamic development of sustainable highway infrastructure projects rather than the static results produce by the quantitative approach.

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