The mean number of text messages sent per month by customers of a cell phone service provider is 1,850, and the standard deviation is 800. Find the z-score associated with 3,000 messages sent.
A)z = 2.75
B)z = 1.44
C)z = -1.44
D)z = 1.19
E)z = 40.66

Question

The mean number of text messages sent per month by customers of a cell phone service provider is 1,850, and the standard deviation is 800. Find the z-score associated with 3,000 messages sent. ​
A)z = 2.75
B)z = 1.44
C)z = -1.44
D)z = 1.19
E)z = 40.66

Quizplus · Accepted Answer

The z-score is calculated using the formula $z = \frac{(X - \mu)}{\sigma}$, where $X$ is the value in question, $\mu$ is the mean, and $\sigma$ is the standard deviation. Plugging in the given values: $z = \frac{(3000 - 1850)}{800} = \frac{1150}{800} = 1.4375$, which rounds to 1.44.

The Mean Number of Text Messages Sent Per Month by Customers