Choosing a method of data collection
No single method suits every study. Choose by the nature and purpose of the study, the respondents, and the time, money and precision you have.
Methods compared
| Method | Best when | Limitation | Nutrition example |
|---|---|---|---|
| Observation | Behaviour can be seen directly; people may not report it truly | Slow; observer bias; cannot see past events or feelings | Watching plate waste after a mid-day meal |
| Personal interview | Detailed answers are needed; respondents may not read | Costly; interviewer bias | Diet history of a diabetic patient |
| Questionnaire (post or online) | Respondents are literate and spread out | Low response; no one to explain doubts | Online survey of college students' snacking |
| Schedule (filled by an enumerator) | Large field survey; respondents may be illiterate | Needs trained enumerators; costly | Household food consumption survey in a village |
| Measurement | Objective data on nutritional status are needed | Needs equipment, skill and consent | Height, weight and Hb of school girls |
Factors in choosing a method
- Nature, scope and objective of the study: feelings and reasons need interviews; behaviour may need observation.
- Respondents: literacy, age, language and how spread out they are. Children and illiterate mothers need an interviewer.
- Funds: online questionnaires are cheap; field schedules and lab tests cost more.
- Time available: a mailed questionnaire may take weeks to come back.
- Precision required: weighing food is more precise than asking people to recall it.
- Researcher's skills and the community's acceptance of the method.
Deciding on a method
Dietary methods: a nutrition special
| Method | What it gives | Note |
|---|---|---|
| 24-hour recall | Food eaten in the previous 24 hours | Quick; depends on memory; repeat on 2-3 days for a usual intake |
| Food frequency questionnaire | How often foods are eaten (daily, weekly, rarely) | Shows the usual pattern; amounts are rough |
| Diet history | Usual diet over a longer period | Needs a skilled interviewer |
| Weighed food inventory | Exact amounts, weighed | Most accurate; slow, and people may change what they eat |
For a diet survey of college students, a self-filled questionnaire works because they are literate. For mothers in a village, an interview schedule is better. Pair a dietary method with anthropometry or an Hb test for objective proof.
2 marks: “List any four methods of collecting primary data.” Observation, interview, questionnaire, schedule (and direct measurement).
5 marks: “What factors decide the choice of a method of data collection?” Kothari's four (nature and object of enquiry, funds, time, precision) plus the respondents' literacy and the researcher's skill, each with an example.
10 marks: “Explain the methods of collecting primary data and how you would select a suitable method for a diet survey.” Describe each method with merits and limits, explain the factors in choosing, add dietary methods, and justify a choice for a named group.
Kothari's four factors: "Never Forget The Purpose" = Nature of enquiry, Funds, Time, Precision.