# . A number of individuals were asked how many e-mails that they sent per day.

9. A number of individuals were asked how many e-mails that they sent per day. The results are summarized in the following grouped frequency distribution.

Emails (per day) Frequency

8 – 12 3

13 – 17 34

18 – 22 31

23 – 27 8

28 – 32 27

a) How many emails were sent?

b) Approximate the mean weight.

c) Determine the class width.

d) Determine the boundaries of the class 18 – 22.

e) Determine the midpoint of each class and use the midpoint to estimate the standard deviation of the frequency distribution.

10. Binomial Distribution –

A. A restaurant has found that about 20% of the diners with reservations do not show up. Suppose that 12 reservations parties are made.

a) Write the binomial probability function for this experiment.

b) Calculate the binomial coefficient then calculate the probability that exactly 4 of the reservation parties show up. Would we expect this probability to be large or small? Why?

c) If the manager wishes to determine how the probability that three or more will show up, what probabilities need to be added? (Do not calculate)

d) Find the mean of this binomial distribution and explain what this number tells us in this context

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