Comments on PERT

• When a Bell curve is skewed to the left, the value of 'Mean' can be significantly higher than the 'Most Likely' estimate
• You can add the 'Most Likely' durations on a critical path to get the total most likely time. You can do the same with the 'Mean's to get a weighted average estimated time for the project
• However, to get the overall 'Standard Deviation', you must take the square root of the sum of the variances
• Other types of distribution, (triangular, square, etc) have the same approach, but different formulae
• The Bell curve is the most used because it is typically closest to real life

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