Explanation:

The median is a measure of central tendency that represents the middle value of a dataset. In a grouped frequency distribution, the data is organized into intervals or classes, and each interval has a corresponding frequency.

Definition of N:
In the formula for finding the median of a grouped frequency distribution, N represents the total frequency of the dataset. It is the sum of all the frequencies in the distribution.

Interpretation:
The total frequency, N, is important in finding the median because it gives us the information about the number of data points in the distribution. By knowing the total frequency, we can determine the position of the middle value in the dataset.

Steps to find the median:
To find the median of a grouped frequency distribution, follow these steps:

1. Calculate the cumulative frequency: Cumulative frequency represents the running total of the frequencies. It is obtained by adding up the frequencies of each class from the starting class to the desired class.

2. Identify the class interval that contains the median: The class interval that contains the median is the one where the cumulative frequency exceeds or is equal to (N/2), but the cumulative frequency of the previous interval is less than (N/2).

3. Determine the median class: The median class is the class interval identified in step 2.

4. Use the formula: The median can be calculated using the formula:
Median = L + ((N/2) - CF) * (C/I)

- L represents the lower limit of the median class.
- N represents the total frequency.
- CF represents the cumulative frequency of the class preceding the median class.
- C represents the frequency of the median class.
- I represents the width of the median class.

Importance of N:
The total frequency, N, is crucial in the formula for finding the median because it allows us to determine the position of the middle value in the dataset. Without knowing the total frequency, it would be impossible to accurately calculate the median for a grouped frequency distribution.

Conclusion:
In a grouped frequency distribution, the total frequency, N, is used in the formula to calculate the median. It provides the necessary information to determine the position of the middle value in the dataset. Therefore, option 'A' - total frequency is the correct answer.