a mean of 57 and a standard deviation of 3. Using the 68-95-99.7 rule, what is the approximate percentage of lightbulb replacement requests numbering between 57 and 66?

Answer 1

The 68-95-99.7 rule says that (from the mean) ± 1 standard deviation (σ) is 68%, ±2 σ is 95%, and ±3 σ is 99.7%.

From a mean of 57, +1σ would be 57+3 or 60, +2σ would be 63, and +3σ would be 66. So we need 57 + 3σ

If ±3σ is 99.7%, then +3σ is 99.7/2 or 49.85%