Answer:
A. -1
Step-by-step explanation:
We have been given that a shipment of beach balls with a mean diameter of 28 cm and a standard deviation of 1.3 cm is normally distributed.
Since z-score represents that a raw score is how many standard deviation above or below mean.
To solve our given problem we will use z-score formula.
\(z=\frac{x-\mu}{\sigma}\), where,
\(z=\text{z-score}\),
\(x=\text{Raw score}\),
\(\mu=\text{Mean}\),
\(\sigma=\text{Standard deviation}\).
Upon substituting our given values in z-score formula we will get,
\(z=\frac{26.7-28}{1.3}\)
\(z=\frac{-1.3}{1.3}\)
\(z=-1\)
Therefore, a beach ball with a diameter of 26.7 cm differs -1 standard deviation from the mean and option A is the correct choice.
