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Averages

Averages​

Core formulas:

Average = sum / count
Sum = average * count
New average = old average + change in total / count

Weighted average:

Combined average = (n1*a1 + n2*a2) / (n1 + n2)

Replacement:

If average of n numbers changes by d:
Total change = n*d
New item - old item = n*d

Fast checks:

  • Average must lie between minimum and maximum.
  • For consecutive equally spaced numbers, average is the middle value.
  • If average is closer to one group average, that group has more weight.

Deviation method:

Average = assumed average + sum of deviations / count