In a mid-size company, the distribution of the number of phone calls answered each day by each of the 12 receptionists is bell-shaped and has a mean of 60 and a standard deviation of 3. Using the
empirical rule, what is the approximate percentage of daily phone calls numbering between 57 and
63?

Prob ( 41 <= X <= 77) =

Prob ( (41-59)/9 <= Z <= (77-59)/9 ) =  <--- changes to z scores

Prob ( -18/9 <= Z <= 18/9 ) =

Prob ( -2 <= Z <= 2) =

Prob ( z<=2) - Prob(Z<=-2)  =       <--- by property of the normal bell curve

=  0.9772 - 0.0228   <--- per the normal distribution table

= 0.9544

Step-by-step explanation:

make sense ?

00

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