One of the characteristics of the normal curve is that the area under the curve is 100%. By
symmetry, 50% of the area lies above the mean and 50% lies below the mean. We need this
characteristic to answer the following type of question:
What area lies under the normal curve from u + 1σ to as far to the right as the curve goes?
Since the tails of the curve approach, but never touch the horizontal base line, the curve extends
infinitely far in both directions and we have to answer the question indirectly. We do know that
half of the area lies to the right of the mean. The area from u to 1σ we know is 34%. The
difference 50% - 34% = 16% is that area in the right half of the curve that lies above u + 1σ.
The shaded area is referred to as the right tail of the curve.