Explanation:
Open-end class interval is the interval that does not have a fixed upper or lower limit. These intervals are represented by a symbol like (<) or="" (="">). It is difficult to find the arithmetic mean (A.M) for open-end class interval because the exact values of upper and lower limits are not known. However, we can find the frequency of data even if the class interval is open-end. The following points explain why it is difficult to find the arithmetic mean for open-end class interval.

Difficulty in finding upper and lower class limits:
In open-end class interval, the exact values of upper and lower limits are not known. Therefore, it is difficult to determine the mid-value of each class interval. The mid-value is used to find the arithmetic mean of a set of data.

Difficulty in calculating the summation of mid-values:
The formula for calculating the arithmetic mean of data is the sum of all mid-values divided by the total frequency of data. In open-end class interval, it is difficult to calculate the summation of mid-values because the exact mid-value of each class interval is not known.

Difficulty in calculating the total frequency:
The total frequency of data can be calculated even if the class interval is open-end. The frequency of each class interval can be determined by counting the number of observations falling in that interval. However, the arithmetic mean cannot be calculated without the mid-values of each class interval.

Conclusion:
In conclusion, it is difficult to find the arithmetic mean for open-end class interval because the exact values of upper and lower limits are not known. However, the frequency of data can still be determined even if the class interval is open-end.

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