NCERT Solutions Class 9 Maths Chapter 14 — Statistics

Solution:

Step 1: Primary data refers to data collected by the investigator himself/herself for a specific purpose directly from the source.

Step 2: When a class teacher conducts a test and records the marks, they are collecting this data firsthand, making it primary data.

Step 3: Options A, B, and D describe data that has already been collected, compiled, or published by others, which falls under secondary data.

Solution:

Step 1: Raw data is data that has not been processed, organized, or analyzed in any way.

Step 2: It is the initial form in which data is collected directly from the source.

Step 3: Arrayed data is raw data arranged in ascending or descending order, while grouped data is organized into classes or intervals.

Solution:

Step 1: The frequency of an observation or category is simply the count of how many times it appears or occurs in the data set.

Step 2: In this scenario, 'Cricket' was chosen by 8 students.

Step 3: Therefore, the frequency of 'Cricket' is 8.

Solution:

Step 1: The given class interval is 10-19. This is an inclusive class interval, meaning all values from 10 up to and including 19 are part of this class.

Step 2: The formula for the class size of an inclusive interval is (Upper Limit - Lower Limit + 1).

Step 3: Applying the formula: Class size = (19 - 10 + 1) = 9 + 1 = 10.

Solution:

Step 1: The class mark is the representative value of a class interval.

Step 2: It is calculated as the average of the upper and lower limits of the class interval.

Step 3: Formula: Class Mark = (Lower Limit + Upper Limit) / 2. This definition makes it the midpoint.