It is estimated that about 99.7% of observations are expected to fall between 3 standard deviations below and above the mean. A normal curve. The x-axis has values mu minus 3 sigma, mu minus 2 sigma, mu minus sigma, mu, mu + sigma, mu + 2 sigma, mu + 3 sigma. Between mu minus 3 sigma and mu minus 2 sigma is question mark. Between mu minus 2 sigma and mu minus sigma is 13.5 percent. Between mu minus sigma and mu is 34 percent.

What percent of observations are expected to fall between 2 and 3 standard deviations above (or below) the mean?

5%
4.7%
2.5%
2.35%