Answer:
15.87% of the invoices were paid within 15 days of receipt
Step-by-step explanation:
An invoice was paid an average of 20 days after it was received.
Mean = [tex]\mu = 20[/tex]
Standard deviation = [tex]\sigma = 5[/tex]
Now we are supposed to find what percent of the invoices were paid within 15 days of receipt i.e.P(x<15)
Formula : [tex]Z=\frac{x-\mu}{\sigma}[/tex]
At x = 15
Substitute the values
[tex]Z=\frac{15-20}{5}[/tex]
[tex]Z=-1[/tex]
Refer the z table for p value
So, p value = 0.1587
So, 15.87% of the invoices were paid within 15 days of receipt