Compare Standard Deviation The Obama vacations have cost an average of 4 million and a standard deviation of 5 million. The Bush vacations have cost an average of 3 million and a standard deviation of 2 million. What is more unusual: an Obama vacation that costs 5 million or a Bush vacation that cost 1 million? What I think: I don't know what "more unusual" means in statistics. I tried to solve this problem by comparing the standard deviation and the z-interval.

Bush's vacation costing $1,000,000 is a $1,000,000 less than average, for Bush: a full standard deviation lower than average. Obama's vacation costing $5,000,000 is only 1/5 th of a standard deviation higher than average.

So Bush's vacation cost _deviated more_ from the average, with respect to for Bush, than did Obama's (with respect to Obama's average costs), i.e., Bush's vacation cost was the more _unusual_ in the sense that his vacation costs deviated more than is typical for Bush, than did Obama's vacation cost from what is typical for Obama.