This next section takes advantage of the literature review, category analysis and initial analysis sections and builds on these to construct a number of research questions to be explored in this study.
From the literature, the concept of analysing each category as a separate entity versus
analysis of the categories in one combined model has been discussed. In order to formally test and compare these different models, the research questions will be first considered for
separate categories. Following this, research questions relating to the combined category analysis will be discussed and presented. This is done in this way as it presents a logical way of building the analysis.
The literature review demonstrates the benefits of a behavioural consumer analysis approach to consumer understanding, especially when considering actual consumer behaviour versus planned consumer behaviour. Within the behavioural analysis literature, the Behavioural Perspective Model is the most developed in terms of understanding radical behaviourism (Wells, 2014) hence this model is employed as a theoretical framework for the study. The flexibility of the model has allowed numerous studies in multiple categories and geographies (e.g. Foxall, 2016a, b, 2017; Foxall and James, 2003; Foxall and Schrezenmaier, 2003; Foxall
et al., 2004; Foxall et al., 2006; Oliveira-Castro et al., 2005; Romero et al., 2006).
The literature suggests the price of the product is an important aspect of the behavioural economic aspects of consumer understanding. The negative relationship between price and purchase behaviour is prevalent in behavioural economics and within the BPM framework (e.g. Oliviero-Castro et al., 2006; Broadbent, 1980; Gabor, 1988; Nagle, 1987; Roberts, 1980; Telser, 1962; Chang, 2007; Foxall et al., 2013). While this is not new research, it is important for any new consumer research to assess whether price remains an important variable in the consumer behaviour model. Also, to omit the price variable will cause the model to attempt to compensate for the effect through other variables within the model, hence distorting the
true effect of these variables included within the model. Also, assessing how the price
elasticity of demand may, or may not vary under a more complex model will be an interesting addition to the subject. Hence the first research question addresses this area and for each category model, the following research question is considered. The research question is subdivided into each of the four categories.
RQ1: Does the average price of the products within the category influences consumer economic behaviour?
Past studies have shown the psychological variables of the BPM, in terms of the
Informational and Utilitarian reinforcement variables are influencing consumer behaviour. This is maintained within this study through the following RQ.
RQ2: Are the BPM psychological variables accounting for consumer behaviour for each category. the nature of the supermarket own brand impacting consumer behaviour of the category through differing behaviour at a consumer psychological level, either at a utilitarian and/or informational reinforcement level?
The literature suggests brands which are considered as a higher equity are considered to have a higher informational and utilitarian reinforcement associated with them and the nature by which the BPM had allocated informational and utilitarian reinforcement scores underline this principle. However, the literature also suggests the prevalence of supermarket own brands may have a different influence on how consumers view the brand. The results of the category analysis show the differing nature of the supermarket own brand in terms of the informational and utilitarian reinforcement responses. This could mean a different strategy is required when marketing and retailing these types of brands.
This research aims to build on previous studies by exploring the nature of the psychological impact of products being formally branded as supermarket own brands and any impact the utilitarian and/or informational reinforcement may have on consumer purchase patterns. The BPM’s flexibility lends a suitable framework for exploring this concept and hence the following category specific research questions are constructed.
RQ3: Is the nature of the supermarket own brand impacting consumer behaviour of the category through differing behaviour at a consumer psychological level, either at a utilitarian and/or informational reinforcement level?
In a similar fashion to RQ3, the seasonal pattern of the Christmas week has a negative effect on total category volume, as seen in the category analysis. However, it is not clear whether this difference is due to changes in consumer psychology attitude within the seasonal period or a more general decrease in category purchase through less consumption and less shopping days during the period. Hence this research aims to test this by seeking to understand whether consumer psychology attitudes to informational and utilitarian reinforcement change within the Christmas period. Hence RQ4 is constructed for each category in turn.
RQ4: Is the seasonal Christmas week impacting consumer behaviour within the category, through different levels of utilitarian and/or informational reinforcement during the Christmas seasonal week?
The next research area focusses on how the structural development of the model itself within the BPM framework. The literature has discussed the potential advantages of a hierarchical structure to the model and this structure is also appealing from a theoretical perspective. The argument is the data follow a hierarchical structure where purchase is located within
household, hence questioning the assumption of independence made when modelling the data in a non-hierarchical structure. Therefore, this study will also construct the model within a hierarchical framework using the BPM theoretical framework. This will enable comparisons to be drawn between the model performance and the interpretation of the variables from a hierarchical and non-hierarchical framework. Hence RQ5 is structured as follows:
RQ5: Will the modelling of the category within the BPM structure benefit from a hierarchical model structure? What differences in interpretation would be included versus a non-hierarchical framework?
The nature of the Bayesian estimation employed within this study opens the discussion on what nature the prior distribution should take. The study will incorporate both vague prior distributions and informative prior distributions to ascertain any differences this brings to each of the category models. Hence RQ6 follows.
RQ6: How will Bayesian inference utilizing informative and vague priors impact the predictive nature of the model and the interpretation of the parameters?
The next area of research originates from the analysis of the cross-category consumption observed by households. Households are predominantly purchasing from more than one category during the year. This questions the assumption of independence within household, between category purchases. Hence a better consumer understanding may be obtained through looking at all purchases from all four categories in one combined model.
This combined category may be considered in the form of two structures as discussed in the literature. The pooled structure allocated a parameter value to each variable across category whilst a fixed effect model allocates a parameter value variable within category. The
advantages of both methods have been discussed and appropriate research questions are now constructed. The research questions are therefore formulated as set forth:
RQ7: Does a combined category model, incorporating all four categories in one model, utilising a pooled parameter structure help the interpretation of consumer behaviour both from a model diagnostic and interpretation perspective? Or does a combined category model, incorporating all four categories in one model, utilising an offset parameter structure help the interpretation of consumer behaviour both from a model diagnostic and
interpretation perspective?
Finally, given the data will be modelled in the first place as four separate categories and thereafter as one combined model, incorporating all categories, it will be interesting to test which structure provides the better model in terms of diagnostics and ease of interpretation. Hence RQ8 is as such.
RQ8: How does the diagnostic measured and parameter estimation differ between treating the data as four separate category models versus one combined cross-category model.