**Primary data**

Primary data refers to the data that is collected firsthand by the researcher for a specific purpose or study. It is original data collected directly from the source, and it has not been previously collected or published by anyone else. In this case, the student collected information about the number of school-going children in a locality consisting of a hundred households.

**Explanation**

The student collected the data himself, directly from the households in the locality. He went door to door and gathered information about the number of school-going children in each household. This collection of data is considered primary data because it is original and collected firsthand by the student for his specific purpose of studying the number of school-going children in the locality.

**Characteristics of Primary Data**

Primary data has certain characteristics that differentiate it from other types of data:

1. **Originality:** Primary data is collected directly from the source, making it original and unique to the researcher's study.

2. **Firsthand Information:** Primary data provides firsthand information as it is collected directly by the researcher, ensuring accuracy and relevance to the study.

3. **Specific Purpose:** Primary data is collected for a specific purpose or research study, allowing the researcher to tailor the data collection process to their needs.

4. **Reliability:** Since primary data is collected firsthand, it is generally considered to be more reliable and accurate compared to secondary data.

5. **Time-consuming:** Collecting primary data can be a time-consuming process as it requires direct interaction with the source and may involve conducting surveys, interviews, or observations.

In conclusion, the data collected by the student about the number of school-going children in a locality consisting of a hundred households is considered primary data because it is original, collected directly by the student, and specifically gathered for his study.

D.Grouped data