While computing mean of grouped data, we assume that the frequecies are

Options

A. evenly distributed over all the classes
B. centred at the class marks of the classes
C. centred at the upper limits of the classes
D. centred at the lower limits of the classes

Explanation

To solve the question regarding the assumption made while computing the mean of grouped data, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Grouped Data**:
Grouped data is data that has been organized into classes or intervals. Each class has a frequency that indicates how many data points fall within that interval.

2. **Class Marks**:
The class mark is the midpoint of a class interval. It is calculated by taking the average of the upper and lower limits of the class. For example, for the class interval 40-50, the class mark would be (40 + 50) / 2 = 45.

3. **Frequency Assumption**:
When calculating the mean of grouped data, we assume that the frequencies are evenly distributed across the class intervals. This means we consider that all the data points within a class interval are centered around the class mark.

4. **Options Analysis**:
The question provides four options regarding where the frequencies are centered:
- A) Evenly distributed over all classes centered at class marks
- B) Centered at upper limits of the class
- C) Centered at lower limits of the class
- D) None of the above

5. **Correct Answer**:
Based on our understanding, the correct answer is that the frequencies are centered at the class marks of the classes. This aligns with option A.

### Final Answer:
The correct option is A) Evenly distributed over all classes centered at class marks.