A normal distribution has a mean of µ = 70 with σ = 12.If one score is randomly selected from this distribution,what is the probability that the score will be less than X = 55?
A)0.3944
B)0.1056
C)0.8944
D)0.7888

Question

A normal distribution has a mean of µ = 70 with σ = 12.If one score is randomly selected from this distribution,what is the probability that the score will be less than X = 55?​
A)​0.3944
B)​0.1056
C)​0.8944
D)​0.7888

Quizplus · Accepted Answer

To find the probability of X being less than 55, we need to standardize the score using the z-score formula:
z = (X - µ) / σ
z = (55 - 70) / 12
z = -1.25
We can then look up the probability of a z-score being less than -1.25 in the standard normal distribution table or use a calculator. The answer is approximately 0.1056, which corresponds to choice B.

A Normal Distribution Has a Mean of µ = 70