It depends on the type of data you want to collect and the phenomenon you want to look at. For the city's restaurant market, do you want to assess the profitability or the total services (from restaurant owners to employees, as well as consumer behaviours)?

It depends what you want to assess. You can conduct survey using questionnaires to measure consumers preferences and opinions regarding restaurant choices, frequency of dining out, cuisines preferences, etc.

Principles: Ensure the questions are clear, unbiased, and represent all aspects of dining preferences.

First, you need to define your research objectives. Otherwise, no one can guide you.

Objectives are:

How do I find out why a guest chose this particular restaurant? How appropriate is it to study the motives of visiting and what marketing tools and how they work for different generations: X,Y,Z

You may require to use qualitative methods to explore those variables motivates one for visiting a restaurant. If need arises go for further study to establish your findings using quantitative analysis.

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