In the professors note they say

We build a 95% confidence interval around the expected return

If teh desired return falls in the 2.5% lower tail of the distribution the client can be 95% confident that the minimum will not be violated

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if you are in the lowest 2.5 tail, does not that leave at least 97.5% of the values greater than you. basiclly the goal will be met at least 97.5% of the time and up to 99.9999% of the time, depending on how much into the tail the desired return is…