Question

Find the class mark of $ 80-90 $ .

Answer 1

Hint: The class mark, also called the central value of the class, is the average value of the lower and the upper limit of the class interval.To refer to the formula, build the formula based on the definition.

Complete step-by-step answer:
Now, according to the question we need to find the class mark of the given class.
Class mark is the central value of a class. By definition, it is the average of the upper limit and the lower limit of a given class.
The formula for calculating the class mark is given below:
Class Mark: (actual upper limit + actual lower limit) divided by $ 2 $
For example, if we have a class interval of $ 30-40 $ , the actual upper limit of the class is 40 and the actual lower limit of the class is 30. Therefore the mid value or the class mark of the class is
 $ \dfrac{30+40}{2}=35 $
Accessing raw data is sometimes too expensive computationally. In such cases, class marks are used which is a good approximation of the mean of the class.
In the given question, the given class is $ 80-90 $ .
The actual lower limit of the class is $ 80 $ .
The actual upper limit of the class is $ 90 $ .
The class mark is: $ \dfrac{80+90}{2}=\dfrac{170}{2}=85 $
Hence , $ 85 $ is the answer.
So, the correct answer is “85”.

Note: Note that class mark and class size are different. For a given class interval, class size is the difference between the upper and the lower limits of the class interval whereas class mark is the average or the mid value of the upper and lower class limits.