Question

A set of data items is normally distributed with a mean of 400 and a standard deviation of 60. Find the data item in this distribution that corresponds to the following z-score:
z=3

Answer 1

Answer:

The data item is $X = 580$

Step-by-step explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$, the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

Mean of 400 and a standard deviation of 60.

This means that $\mu = 400, \sigma = 60$

z=3

We have to find X when Z = 3. So

$Z = \frac{X - \mu}{\sigma}$

$3 = \frac{X - 400}{60}$

$X - 400 = 3*60$

$X = 580$

The data item is $X = 580$