
Give the formula for class mark and class size of data.
Answer
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Hint: To get the formula for the class mark and class size, just follow their definitions. The class mark is the average of the upper and lower limit of a class interval and the class size is the difference of the upper and lower limit of a class interval.
Complete step by step answer:
Note: In this question, one might get confused and consider class size as the summation of the upper and lower limits of a given class interval. This is wrong because class size is the difference between the upper and lower limits of a given class interval. Therefore, one must keep this point in mind.
According to the question, we have to get the formula for the class mark and class size.
We know that class mark is the mid-value or central value of a class. It means that it is the average of the actual upper limit and actual lower limit for a given class. It may also be said that the mid value of every class interval is called its class mark.
The class mark can be calculated by the formula, ………………..(1)
For instance, let us consider the class interval 10-20,
The actual upper limit of the given class = 20 ………….(2)
The actual lower limit of the given class = 10 …………(3)
Now, from equation (1), equation (2), and equation (3), we get
Therefore, the class mark for the class interval 10-20 is 15.
We also know that the class size is defined as the difference between the actual upper limit and actual lower of a given class interval.
The class size can be calculated by the formula, ……………………………………(4)
For instance, again let us consider the class interval 10-20,
The actual upper limit of the given class = 20 ………………………………….(5)
The actual lower limit of the given class = 10 ……………………………………(6)
Now, from equation (4), equation (5), and equation (6), we get
Therefore, the class size for the class interval 10-20 is 10.
From equation (1) and equation (4), we have formula for the class mark and class size for a given class interval respectively.
Hence, and .
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