what do you mean by two standard deviation?

Question

I understand standard deviation a bit but not fully so kindly someone explain two standard deviation.

In: 5

Answer 1

According to one survey, American adult males have an average height of 70 inches and a standard deviation of 2.66 inches. That means anyone of height 75.33 inches or above is two standard deviations above the mean (70 + 2.66 + 2.66). In a perfect bell curve, 2.3% of all samples are two std. devs. above the mean, 2.3% of all samples are two std. devs. below the mean, and 95.4% of all samples are within two std. devs. of the mean.