Class mark of the class 90-120

The class mark of a class interval refers to the midpoint or average value of the lower and upper class limits. It is a representative value that helps in summarizing the data in a frequency distribution. In the case of the class 90-120, the class mark can be calculated as follows:

Step 1: Find the lower class limit (LCL)
The lower class limit is the smallest value in the class interval. In this case, the lower class limit is 90.

Step 2: Find the upper class limit (UCL)
The upper class limit is the largest value in the class interval. In this case, the upper class limit is 120.

Step 3: Calculate the class width (CW)
The class width is the difference between the upper class limit and the lower class limit. It gives us the range of values included in the class interval. In this case, the class width can be calculated as:
CW = UCL - LCL = 120 - 90 = 30.

Step 4: Calculate the class mark (CM)
The class mark is the average of the lower and upper class limits. It gives us a single representative value for the class interval. In this case, the class mark can be calculated as:
CM = (LCL + UCL) / 2 = (90 + 120) / 2 = 210 / 2 = 105.

Therefore, the class mark of the class 90-120 is 105.

Summary:
- The class mark of a class interval is the midpoint or average value of the lower and upper class limits.
- It helps in summarizing the data in a frequency distribution.
- The class mark of the class 90-120 can be calculated by finding the lower class limit (90), upper class limit (120), class width (30), and taking the average of the lower and upper class limits (105).

Overall, understanding the concept of class marks is essential in data analysis and interpretation, as it helps in representing the data in a concise and meaningful way.