Introduction:
The coefficient of mean deviation about mean is a measure of the dispersion or variability of a set of numbers around their mean. It is expressed as a percentage and indicates how widely spread out the data points are from the mean value.

Calculation of Mean:
To calculate the mean of a set of numbers, we sum up all the numbers and divide the sum by the total count of numbers. In this case, we are considering the first 9 natural numbers, which are 1, 2, 3, 4, 5, 6, 7, 8, and 9. The sum of these numbers is 45, and since there are 9 numbers, the mean is 45/9 = 5.

Calculation of Deviation:
Deviation refers to the difference between each individual number and the mean. To calculate the deviation for each number, we subtract the mean from the number. For example, for the number 1, the deviation is 1 - 5 = -4. Similarly, for the number 2, the deviation is 2 - 5 = -3. We repeat this process for all the numbers.

Calculation of Absolute Deviation:
The absolute deviation is the absolute value of the deviation. It gives us the magnitude of the difference between each number and the mean, without considering the direction. For example, the absolute deviation for the number 1 is |-4| = 4. We calculate the absolute deviation for all the numbers.

Calculation of Mean Absolute Deviation:
The mean absolute deviation is the average of all the absolute deviations. To calculate it, we sum up all the absolute deviations and divide the sum by the total count of numbers. In this case, the sum of the absolute deviations is 20, and since there are 9 numbers, the mean absolute deviation is 20/9 = 2.22 (rounded to two decimal places).

Calculation of Coefficient of Mean Deviation about Mean:
The coefficient of mean deviation about mean is calculated by dividing the mean absolute deviation by the mean and multiplying the result by 100 to express it as a percentage. In this case, the mean absolute deviation is 2.22 and the mean is 5. Therefore, the coefficient of mean deviation about mean is (2.22/5) * 100 = 44.44% (rounded to two decimal places).

Conclusion:
The coefficient of mean deviation about mean for the first 9 natural numbers is 44.44%. This indicates that, on average, the numbers deviate by 44.44% from the mean value of 5. Higher values of the coefficient indicate a greater dispersion or variability in the data set.