STATISTICS
Frequently Asked Questions
Statistics is the branch of mathematics concerned with collecting, organizing, presenting, analyzing, and interpreting data.
Data is a collection of numerical facts or observations used for analysis.
Data collected directly by the investigator is called primary data.
Data collected from published or already available sources is secondary data.
Unorganized numerical information collected during a study is raw data.
Data arranged into classes or intervals is grouped data.
Data presented as individual observations without grouping is ungrouped data.
The number of times a particular observation occurs is its frequency.
A table showing all observations (or class intervals) along with their frequencies.
A group between two values that defines a range, such as 10–20.
The smallest and largest values in a class interval.
The difference between upper and lower class limits.
Midpoint of a class interval: \(\dfrac{\text{(lower limit} +\text{ upper limit)}}{2}\).
Class intervals where both limits are included.
Class intervals where the upper limit is excluded.
To prepare data for graphs like histograms, which require continuity.
A quick method of counting frequencies using vertical strokes.
Arranging data systematically in tables for clarity.
A graphical representation of categorical data using rectangular bars.
For comparing data across distinct, separate categories.
A graph showing continuous grouped data using adjoining rectangular bars.
Histogram bars touch (continuous data); bar graph bars have gaps (discrete data).
A line graph constructed by joining points plotted at class marks vs. frequencies.
To understand the shape of the data distribution clearly.
Yes, by plotting polygon points on top of the histogram bars.
A simplified method using a convenient number as a reference mean.
The middle observation of an ordered data set.
Bar graph, histogram, and frequency polygon.
Running total of frequencies up to a class.
To ensure accurate and fair visual comparison of data.
Because it represents the central value of each class interval.
It shows the distribution and spread of continuous data clearly.
It highlights comparison among discrete categories.
To present data visually for easy understanding.
Use correct scale, equal class sizes, accurate labeling, and neat plotting.
Wrong scaling can mislead interpretation of data.
Collecting reliable and relevant data.
Drawing meaningful conclusions from analyzed data.
Representing large data in compact form.
Number of students in a class.
Heights of students.
Misread graphs, ignoring scales, mixing continuous and discrete data incorrectly.
Helps in decision-making, planning, forecasting, and analyzing trends.
To analyze exam results, performance, attendance, and growth.
For demand analysis, sales forecasting, and market surveys.
No, formulas for grouped median and mode are not part of the Class 9 syllabus.
Converting raw data ? frequency table ? bar graph ? histogram ? frequency polygon.
Frequency tables, bar graphs, histograms, frequency polygon, mean, median, mode.
Graphs (bar graph, histogram, frequency polygon).
Constructing frequency tables, drawing graphs, and finding mean/median/mode.
Check totals, use correct class marks, follow formula carefully.
Keep class intervals continuous and bar widths equal.
Look for the class interval with the highest frequency.
