Averaging with a tolerance

Question

I'm having some issues with trying to average some values. Lets say (for this example) that earthquakes are measured on a scale of 1-6. No earthquake can be stronger than a 6 and you want to calculate on average strength of the earthquakes in one area. For instance you have a single 6 rated earthquake and three 3 rated earthquakes. The way i'm calculating it, i'm getting values that make no sense. I'm weighing the earth quakes by the corresponding values saying that a single earthquake is like a 6 in my average and the three 3's are equivalent to 9 however when you take this average you get 7.5 which obviously makes no sense since no earthquake can be weighted more then a 6??? I know this is vague and i'm probably making no sense but if you do understand the jargon i'm trying to ask, could you please answer. Thank you.

Answer 1

To calculate the mean, you add all the values and divide by the number of them. In your example, the mean is $\frac {6+3+3+3}{4}=\frac{15}4=3.75$, which is well within range. When you count the number, repeated values must be counted over again.