Choosing the suitable questionnaire for a research study depends on: Group of answer choicesThe primary data required and the data collection method usedThe sampling sizeThe secondary data needed and the sampling sizeAll of the above

Choosing the suitable questionnaire for a research study depends on the primary data required and the data collection method used.

Here's why:

1. The Primary Data Required: The type of data you need for your research will greatly influence the kind of questionnaire you choose. For instance, if you need qualitative data, you might opt for open-ended questions. On the other hand, if you need quantitative data, you might choose a questionnaire with closed-ended questions.

2. The Data Collection Method Used: The way you plan to collect your data also matters. For example, if you're conducting a phone survey, you might need a shorter questionnaire. But if you're conducting a mail or online survey, you could potentially use a longer questionnaire.

The sampling size and the secondary data needed might influence other aspects of your research design, but they don't directly determine the type of questionnaire you should use. Therefore, the correct answer is "The primary data required and the data collection method used".