Answer:
P(61≤ X≤94) = 49.85%
Step-by-step explanation:
From the given information:
The mean of the bell shaped fluorescent light bulb μ = 61
The standard deviation σ = 11
The objective of this question is to determine the approximate percentage of light bulb replacement requests numbering between 61 and 94 i.e P(61≤ X≤94)
Using the empirical (68-95-99.7)rule ;
At 68% , the data lies between μ - σ and μ + σ
i.e
61 - 11 and 61 + 11
50 and 72
At 95%, the data lies between μ - 2σ and μ + 2σ
i.e
61 - 2(11) and 61 + 2(11)
61 - 22 and 61 +22
39 and 83
At 99.7%, the data lies between μ - 3σ and μ + 3σ
i.e
61 - 3(11) and 61 + 3(11)
61 - 33 and 61 + 33
28 and 94
the probability equivalent to 94 is when P(28≤ X≤94) =99.7%
This implies that ,
P(28≤ X≤94) + P(61≤ X≤94) = 99.7%
P(28≤ X≤94) = P(61≤ X≤94) = 99.7 %
This is so because the distribution is symmetric about the mean
P(61≤ X≤94) = 99.7 %/2
P(61≤ X≤94) = 49.85%
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