Final answer:
The mean of a given data is calculated by summing up all the observations and dividing the total by the number of observations.
Step-by-step explanation:
The mean of a given data is calculated by summing up all the observations and dividing the total by the number of observations. Therefore, option a) Sum of observations/Total number of observations is the correct formula to calculate the mean of the observations. For example, if we have observations 5, 7, and 9, the mean would be (5+7+9)/3 = 21/3 = 7.