The smallest entity in the field inquiry is called data.There are two types of data:
(1) Primary Data
(2) Secondary Data

Primary Data:A data collected by the investigator or organisation for his own use is called primary data. The different methods for collecting primary data are as under:

---

---

Personal observation:It is the most reliable method,as the investigator collects the data by personal observation without asking any question.

---

Questionnaires method: When the field of inquiry is large then this is the best method, as it saves time,money and labour. It is also called questionnaires method. The main disadvantage of this method is that it has highest rate of non-response from the individuals lying under the area of study.

---

Personal interview method:THis method is very expensive and prone to personal bias,as the investigator directly asks questions to individuals and collects of data. It is effectively used in natural calamities.

---

Data through enumerator: This method is very expensive but is a reliable method, as the investigator appoints the person who collects the data from the individual.