Question

patient account division has collected data on the age of accounts receivables. The data collected indicate that the age of the accounts follows a normal distribution with mean 34 days and standard deviation 8 days. What proportion of the accounts are between 20 and 30 days old?

Answer 1

Solution :

Given that ,

mean = = 34

standard deviation = = 8

P(20 < x < 30) = P((20 - 34)/ 8) < (x - ) /  < (30 - 34) / 8) )

= P(-1.75 < z < -0.5)

= P(z < -0.5) - P(z < -1.75)

= 0.3085 -0.0401

= 0.2684

The proportion of the accounts are between 20 and 30 days old is 0.2684