Question

The standard normal curve shown below models the population distribution of a random variable. What proportion of the values in the population does not lie between the two z-scores indicated on the diagram? z = -1.2 z = 0.85

Answer 1

31.28%

Explanation:

The z score is used in statistics to determine by how many standard deviations the raw score is above or below the mean. If the raw score is above the mean then the z score is positive while if the raw score is below the mean then the z score is negative. It is given by:

`z=(x-\mu)/(\sigma)`

Given the z score z = -1.2 z = 0.85. From the normally distribution table, the probability that a value falls between z = -1.2 and z = 0.85 = P(z < 0.85) - P(z < -1.2) = 0.8023 - 0.1151 = 0.6872

The proportion of values that do not fall between z = -1.2 and z = 0.85 = 1 - 0.6872 = 0.3128 = 31.28%