The expected (mean)life of a particular type of light bulb is 1,000 hours with a standard deviation of 50 hours.The life of this bulb is normally distributed.Which most closely reflects the probability that a randomly selected bulb would last fewer than 1100 hours?
A)0.4772
B)0.9772
C)0.0228
D)0.5228
E)0.5513

Question

Quizplus · Accepted Answer

To find the probability that a bulb lasts fewer than 1100 hours, we calculate the Z-score for 1100 hours using the formula Z = (X - μ) / σ, where X is the value (1100 hours), μ is the mean (1000 hours), and σ is the standard deviation (50 hours). This gives us Z = (1100 - 1000) / 50 = 2. The probability of a Z-score less than 2 in a standard normal distribution is approximately 0.9772.

The Expected (Mean)life of a Particular Type of Light Bulb