Page 2 - Lesson note -1 -Ch.14 Statistics( Introduction,Presentation of Data)

Data

A systematic record of facts or different values of a quantity is called data.

Data recorded can be two types
1. Measurement data (Quantitative data): Data which has some numeric values like
marks in the examination, age of the student in the class, weight of the students in the
class etc.
2. Qualitative data: Data which can be group according to common properties like
Gender of students in the class, Blood group of the students etc.

Data can be of two types as per there source type- Primary data and Secondary data.
Primary Data: The data collected by a researcher with a specific purpose in mind is
called primary data.
Secondary Data: The data gathered from a source where it already exists is called
secondary data.
Data variable can be many types
1. Discrete: If the data is present in certain values only like Blood group, gender etc.
2. Continuous: If the data can be present in any values from lower point to height
points on the measurement scale like weight of the student, height of the student etc.

Collection of Data

Activity: Divide the students of your class into four groups. Allot each group the work of
collecting one of the following kinds of data:
(i) Heights of 20 students of your class.
(ii) Number of absentees in each day in your class for a month.
(iii) Number of members in the families of your classmates.
(iv) Heights of 15 plants in or around your school.
How did they collect their data in each group?
(i) Did they collect the information from each and every student, house or person
concerned for obtaining the information?
(ii) Did they get the information from some source like available school records?
In the first case, when the information was collected by the investigator herself or
himself with a definite objective in her or his mind, the data obtained is called primary
data.
In the second case, when the information was gathered from a source which already
had the information stored, the data obtained is called secondary data. Such data,
which has been collected by someone else in another context, needs to be used with
great care ensuring that the source is reliable.

Question 1: What are (i) primary data (ii) secondary data? Which of the two—the
primary or the secondary data—is more reliable and why?
Solution:
Primary data: The data collected by the investigator himself with a definite plan in mind
are known as primary data. These data are, therefore, highly reliable and relevant.