I'm not sure I agree. You certainly shouldn't sneakily make the substitution. However, making a "client" aware of options and the associated trade-offs is very

I'm not sure I agree. You certainly shouldn't sneakily make the substitution. However, making a "client" aware of options and the associated trade-offs is very reasonable. Heck, I'd say it's the most professional approach to this problem! It may be that Mary just needed some measure of central tendency, and would be happier with the mean now versus the median in a week. Alternately, she might need the median specifically for some legally-mandated reporting, and only that will do. You'll never know if you don't ask.