In a large sample of customer accounts, a utility company determined that the average number of days between when a bill was sent out and when the payment was made is 32, with a standard deviation of 4 days. Assume the data to be approximately bell-shaped.

(a) Estimate the percentage of bills for which payment was made in greater than 40 days.

(b) Estimate the percentage of bills for which payment was made in less than 28 days.

(c) Estimate the percentage of bills for which payment was made between 24 and 32 days.

Estimate the percentage of bills for which payment was made in greater than 40 days.is 50%
Estimate the percentage of bills for which payment was made in less than 28 days. 100%
Estimate the percentage of bills for which payment was made between 24 and 32 days. can not be found,

We want to calculate what two values will approximately 68% of the numbers of days be.

For a bell shaped distribution, we can apply the 68-95-99.7 rule, which states that approximately 68% of the data will fall within 1 standard deviation from the mean.

Then, for a mean of 30 and standard deviation of 7, we can calculate the two values as:

X1= μ + z.σ = 28 + 1.4 = 32

so Estimate the percentage of bills for which payment was made in greater than 40 days.

32 = 40 + z.4

z = 50%

the percentage of bills for which payment was made in less than 28 days.

32 = 28 + z.4

z = 100%

the percentage of bills for which payment was made between 24 and 32 days.

32 = 32 + z.4

can noy be found

Learn more about Standard deviation:

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