Final answer:
The standard error of the mean can be calculated by dividing the population standard deviation by the square root of the sample size.
Step-by-step explanation:
The standard error of the mean can be calculated using the formula:
Standard Error (SE) = Population Standard Deviation / √Sample Size
In this scenario, the population standard deviation is 18 (since the variance is 324), and the sample size is 81. Therefore, the standard error of the mean is:
SE = 18 / √81 = 18 / 9 = 2