The mean of a normal probability distribution is 460; the standard deviation is 18.about 68% of the observations lie between what two values? about 95% of the observations lie between what two values? practically all of the observations lie between what two values?

As per given , we have

,

i.e. About 68% of the observations lie between ( and )

i.e. About 68% of the observations lie between ( and )

About 68% of the observations lie between 442 and 478.

i.e. About 95% of the observations lie between ( and )

i.e. About 95% of the observations lie between ( and )

About 95% of the observations lie between 424 and 496.

i.e. Practically all of the observations lie between ( and )

i.e. Practically all of the observations lie between ( and )

Practically all of the observations lie between 406 and 514.

from the figure we get,

the x axis shows   the months and,

the y-axis shows the number of satisfied customer.

each line or each cell in upward direction (y-axis) shows 500.

the appropriate scale for the y - axis is: -

a = 2000 customers

b = 4000 customers

c = 6000 customers

d = 8000 customers

e = 10000 customers

f = 12000 customers

g = 14000 customers