Question

The average number of chocolate chips in a particular brand of chocolate chip chewy cookie is 19. The standard deviation is 26. Assuming that the number of chocolate chips per cookie is normally distributed, what percentage of cookies would have between 13.8 and 24.2 chips?

Answer 1

Average number of chips u = 19

standard deviation sd = 2.6

for chips quantity between 13.8 and 24.2, fist calculating Z values

Z = (X-u)/sd

For 13.8, Z = (13.8 - 19)/2.6 = -2

For 24.2, Z = (24.2 - 19)/2.6 = 2

So, using Z-table, probability Z between (-2 to 2) is approximately 95%