The mean of a normal distribution is 50 and 5% of the values are
greater than 60. Find the standard deviation of this distribution.
(Given the area under standard normal curve between z = 0 and
z = 1.64 is 0.45)
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Answer:
μ = 50q
We need to find σ.
Let X be a random variable having normal distribution.
It is given that 5% of the values are greater than 60. This means P(X > 60) = 0.05. Which means P(X ≤ 60) = 1 - P(X > 60) = 1 - 0.05 = 0.95
If we normalise X, then it will become z = (X-μ)/σ.
We need to find value of z, such that P(z) = 0.95
We can use a table of normal distribution and values. By doing so, we find that z = 1.645
z = (X-μ)/σ.
Hence σ = (X-μ)/z = (60–50)/1.645 = 10/1.645 ≈ 6.079
Step-by-step explanation:
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