medium difficulty5 min

Modal class

The modal class is the class interval with the highest frequency in grouped data.

In one line: Modal class means the class that appears most often.

Understand it

In grouped data, we cannot always identify the exact mode immediately. The modal class gives the interval where the mode is likely to lie. It is the class with the maximum frequency, and it is the starting point for the mode formula.

Example

If frequencies are 3, 7, 12, and 5, then the class with frequency 12 is the modal class.

Formula and rule

Modal class = the class interval with maximum frequency; it is used in the grouped-data mode formula.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

For class intervals 0-10, 10-20, 20-30, 30-40 with frequencies 4, 9, 15, 7, the class 20-30 is the modal class because 15 is the largest frequency.

Method you can reuse

1Look at all frequencies.
2Find the greatest frequency.
3The corresponding class interval is the modal class.
4Use it in the mode formula if required.

Visual tip

Highlight the highest bar or tallest frequency in the table to identify the modal class quickly.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

What makes a class interval the modal class?

Think first, then show answer

A class interval becomes the modal class when it has the highest frequency among all the class intervals in the table. It shows where the data is most concentrated.

Common wrong answer

A common wrong answer is to choose a class because its interval looks central, even when its frequency is not the highest.

Don't mix this up

Students sometimes choose the class with the widest interval instead of the class with the highest frequency.

Exam tip

Before using the mode formula, mark the class that has the highest frequency; that is the modal class.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Students may be asked to identify the modal class before computing the mode of grouped data.

1
Enough for 1 mark
The modal class is the class interval with the highest frequency in grouped data.
2
Add for 2 marks
Example: If frequencies are 3, 7, 12, and 5, then the class with frequency 12 is the modal class.
3
Add for 3 marks
In grouped data, we cannot always identify the exact mode immediately.

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