Question 862894
<pre>
That's the same as the mean of a binomial event with

n=15, p={{{1/2}}}

E(X) = mean(X) = np = {{{(15)(1/2)}}} = {{{7.5}}}

[Even though you would never really EXPECT to ever get {{{7.5}}} tails,
that's about what you would expect to AVERAGE getting, if, say, you
flipped the coin 15 times every day for several years, and kept a running
average of how many tails you got daily.]

Edwin</pre>