Lifetime - bell curve

Laser lifetime follows a normal distribution with a mean of 7000 hours and a standard deviation of 600 hours. What is the probability that the laser will fail before 6000 hours? What is the probability that the laser will last at least 7500 hours?

Correct answer:

p₁ =  0.0478
p₂ =  0.2023

Step-by-step explanation:

$$\begin{gathered} \mu =7000\text{h} \\ \sigma =600\text{h} \\ {p}_1=N(x<6000,\mu ,\sigma ) \\ {p}_1=0.0478 \end{gathered}$$

Use the normal distribution table.

$$\begin{gathered} p_1=N(x>7500,\mu ,\sigma ) \\ {p}_2=0.2023 \end{gathered}$$

Use the normal distribution table.

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