Question

find the area between x=21 and x=24 under distribution curve with mean=20 and standard deviation =4

Answer 1

Since μ = 20 and α = 4

P (21 < X < 24) = P (21 - 20 < X - μ < 24 - 20) =

$P\text{ (}\frac{21-20}{4}<\frac{X\text{ -}\mu\text{ }}{\alpha}<\frac{24\text{ - 20}}{4})$

P (21 < X < 24) = P (0.25 < Z < 1)

Use the standard normal table to conclude that:

P (0.25 < Z < 1) = 0.2426