"The median number of Groupons sold to each Groupon customer (someone who has bought anything): 1."
"The median number of Groupons sold to each person on Groupon’s mailing list: 0."
The median doesn't seem like a fair way to measure either of these. Obviously there the distribution of Groupons sold is skewed, so the mean is likely to be much higher than the median. It would probably paint a clearer picture to say "Of the 25% of people on the mailing list that bought something, half bought 1 groupon, and the other half bought on average 3.6 groupons." (numbers are made up)
Obviously a distribution would be best, but for a single number, the mean is better. For example, if groupon says they have 100,000 customers and they will have 200,000 customers next year, and the mean # of groupons per customer is 2.5, then I can compute that they sell 250,000 groupons per year, and if they get 200,000 groupons, they will sell 500,000 groupons per year. The median tells us none of that.
"The median number of Groupons sold to each person on Groupon’s mailing list: 0."
The median doesn't seem like a fair way to measure either of these. Obviously there the distribution of Groupons sold is skewed, so the mean is likely to be much higher than the median. It would probably paint a clearer picture to say "Of the 25% of people on the mailing list that bought something, half bought 1 groupon, and the other half bought on average 3.6 groupons." (numbers are made up)