Answer:
Option A: 3.59% is the correct answer
Step-by-step explanation:
Z-score is used to calculate the probabilities when mean and standard deviation is given.
Given
Mean = μ = 21
SD = σ = 5
We have to find the probability of selling 12 or less water heaters so our x value is 12
x = 12
The z-score of a value is calculated as:
z-score = (x-μ)/σ
Putting the values
[tex]z-score=\frac{12-21}{5} \\=\frac{-9}{5}\\=-1.8[/tex]
Now z-score table will be used to calculate the probability for z= -1.8
So we will go for the row with -1.8 and column 0, which gives us: 0.03593
As we have to calculate the probability in percentage
[tex]=0.03593*100\\= 3.593\%[/tex]
Hence,
Option A: 3.59% is the correct answer
