Answer:
The interval of hours that represents the lifespan of the middle 68% of light bulbs is 1210 hours - 1390 hours.
Step-by-step explanation:
In statistics, the 68–95–99.7 rule, also recognized as the Empirical rule, is a shortcut used to recall that 68%, 95% and 99.7% of the values lie within one, two and three standard deviations of the mean, respectively.
Then,
- P (µ - σ < X < µ + σ) = 0.68
- P (µ - 2σ < X < µ + 2σ) = 0.95
- P (µ - 3σ < X < µ + 3σ) = 0.997
he random variable <em>X</em> can be defined as the amount of time a certain brand of light bulb lasts.
The random variable <em>X</em> is normally distributed with parameters <em>µ</em> = 1300 hours and <em>σ</em> = 90 hours.
Compute the interval of hours that represents the lifespan of the middle 68% of light bulbs as follows:
Thus, the interval of hours that represents the lifespan of the middle 68% of light bulbs is 1210 hours - 1390 hours.