What the standard deviation really tells you is that some set of users were + or - the test average (or arithmeticmean).
标准偏差真正能够告诉您的是，某些用户是高于还是低于平均测试水平(或者算术含义)。
2
Cannily, the Corning researchers simply took the arithmeticmean of the oxide compositions and created a winning combination, known as "1737 glass", with exactly the right density.