Answer:
The z-score associated with the upper boundary of of this price range is -0.25.
Step-by-step explanation:
It is provided that the board of directors for Cosmic Coffee wants to know the price range for the lowest 40% of drink sales.
If <em>X</em> represents the price range of drink sales, then
P (X < x) = 0.40
Consider that <em>X</em> follows a Normal distribution.
To compute the probability of a normally distributed random variable we need to first convert the raw score to the <em>z</em>-scores.
The formula to <em>z</em>-score is:
Then,
P (X < x) = 0.40
⇒ P (Z < z) = 0.40
The value of <em>z</em> for this probability is:
<em>z</em> = -0.25
*Use a <em>z</em>-table.
Thus, the z-score associated with the upper boundary of of this price range is -0.25.