Assume that x has a normal distribution with the specified mean and standard deviation. Find the indicated probability. (Round your answer to four decimal places.)
μ = 39; σ = 15
P(50 ≤ x ≤ 70)

Question

Assume that x has a normal distribution with the specified mean and standard deviation. Find the indicated probability. (Round your answer to four decimal places.)
μ = 39; σ = 15
P(50 ≤ x ≤ 70)

welshfella · Answer

you need  to use the standard normal probability tables

x1 = 50  standard z score  z1 =      50 - 39
                                                       --------   =   0.7333
                                                             15

now calculate z2 in a similar way  (x2 = 70)

welshfella · Answer

you can then read off the area  under the graph from the tables using the z scores

welshfella · Answer

z score  =  x  - m
               ------
                   s

where m = mean and s = standard deviation.

mcm128 · Answer

Thank you for answering! I calculated (70-39)/15 = 2.0666.

mcm128 · Answer

.7333 = .62 on the Z table