题目
A Bell Curve (Normal Distribution) has a mean of − 1 and a standard deviation of . How many integer values are within three standard deviations of the mean?
解析
均值 = -1
标准差 = 1/8
- 均值下1个标准差 = \(-1 - 1/8 = -1\frac{1}{8}\)
- 均值下2个标准差 = \(-1 - 1/8 - 1/8 = -1\frac{2}{8}\)
- 均值下3个标准差 = \(-1 - 1/8 - 1/8 - 1/8 = \boxed{-1\frac{3}{8}}\)
- 均值上1个标准差 = \(-1 + 1/8 = -7/8\)
- 均值上2个标准差 = \(-1 + 1/8 + 1/8 = -6/8\)
- 均值上3个标准差 = \(-1 + 1/8 + 1/8 + 1/8 = \boxed{-5/8}\)
因此,所有在\(-1\frac{3}{8}\)到\(-5/8\)之间的值都处于均值的3个标准差范围内。
在这个区间内,只有1个整数:-1
答案:B