Data are the numerical facts, which originate from the operation of counting or enumerating. For any Statistical investigation, the first stage is data collection and the basic problem is to collect data relating to the subject matter. The person who conducts the statistical investigation is known as an investigator. The persons from whom the information or data are collected are known as the informants. The process of enumerating or counting the items in a systematic and scientific way is known as a collection of data. Data can be quantitative or qualitative. The data which can be counted in a natural way be quantitative data. The data which represents the quality of an individual is known as qualitative data. Types of Data On the basis of sources of data, there are two types of Data: 1. Primary data 2. Secondary data 1. Primary data The data collected for the first time by the investigator or an agent of the investigator is called primary data. The primary data are...