Final answer:
The standard deviation is a measure of variation in a set of data. To find the standard deviation as a percentage of the mean, divide the standard deviation by the mean and multiply by 100.
Step-by-step explanation:
The standard deviation is a measure of the amount of variation or dispersion in a set of data. It is calculated by finding the square root of the variance. In this case, the standard deviation is given as 9 months.
To find the standard deviation as a percentage of the mean, we divide the standard deviation by the mean and multiply by 100. Let's say the mean is represented by X. The standard deviation as a percentage is given by (9 / X) * 100.
For example, if the mean is 30 months, then the standard deviation as a percentage would be (9 / 30) * 100 = 30%.