68% of the data will be within 1 standard deviation
95% of the data will be within 2 standard deviations
99.7% of the data will be within 3 standard deviations
So yes, we can state that 5% or less of the data will be more than 2 standard deviations away from the mean. Of course, statistics is not 100% certain, so this rule is not 100% right all the time. Some exceptions might result, but generally speaking, the results should follow the empirical rule.
