In: Statistics and Probability
Here, μ = 19.5, σ = 0.5, x1 = 19 and x2 = 21. We need to compute P(19<= X <= 21). The corresponding z-value is calculated using Central Limit Theorem
z = (x - μ)/σ
z1 = (19 - 19.5)/0.5 = -1
z2 = (21 - 19.5)/0.5 = 3
Therefore, we get
P(19 <= X <= 21) = P((21 - 19.5)/0.5) <= z <= (21 -
19.5)/0.5)
= P(-1 <= z <= 3) = P(z <= 3) - P(z <= -1)
= 0.9987 - 0.1587
= 0.840
For P(z <= 3) z value is calculated as:
P(z <= -1) z value is calculated from the table as: