Chapter 4: Q20 (page 143)
In Exercises 13–20, express the indicated degree of likelihood as a probability value between 0 and 1.
Death and Taxes Benjamin Franklin said that death is a certainty of life.
The probability that death will occur is 1.
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Exclusive Or The exclusive or means either one or the other events occurs, but not both.
a. For the formal addition rule, rewrite the formula for P(A or B) assuming that the addition rule uses the exclusive or instead of the inclusive or.
b. Repeat Exercise 11 “Fast Food Drive-Thru Accuracy” using the exclusive or instead of the inclusive or.
In Exercises 9–20, use the data in the following table, which lists drive-thru order accuracy at popular fast food chains (data from a QSR Drive-Thru Study). Assume that orders are randomly selected from those included in the table.
McDonald’s | Burger King | Wendy’s | Taco Bell | |
Order Accurate | 329 | 264 | 249 | 145 |
OrderNotAccurate | 33 | 54 | 31 | 13 |
Fast Food Drive-Thru Accuracy If one order is selected, find the probability of getting an order that is not accurate.
In Exercises 25–32, find the probability and answer the questions.. Guessing Birthdays On their first date, Kelly asks Mike to guess the date of her birth, not including the year.
a. What is the probability that Mike will guess correctly? (Ignore leap years.)
b. Would it be unlikely for him to guess correctly on his first try?
c. If you were Kelly, and Mike did guess correctly on his first try, would you believe his claim that he made a lucky guess, or would you be convinced that he already knew when you were born?
d. If Kelly asks Mike to guess her age, and Mike’s guess is too high by 15 years, what is the probability that Mike and Kelly will have a second date?
In Exercises 9–20, use the data in the following table, which lists drive-thru order accuracy at popular fast food chains (data from a QSR Drive-Thru Study). Assume that orders are randomly selected from those included in the table.
McDonald’s | Burger King | Wendy’s | Taco Bell | |
Order Accurate | 329 | 264 | 249 | 145 |
OrderNotAccurate | 33 | 54 | 31 | 13 |
Fast Food Drive-Thru Accuracy If two orders are selected, find the probability that they are both from Burger King.
a. Assume that the selections are made with replacement. Are the events independent?
b. Assume that the selections are made without replacement. Are the events independent?
In Exercises 25–32, find the probability and answer the questions. YSORT Gender Selection MicroSort’s YSORT gender selection technique is designed to increase the likelihood that a baby will be a boy. At one point before clinical trials of the YSORT gender selection technique were discontinued, 291 births consisted of 239 baby boys and 52 baby girls (based on data from the Genetics & IVF Institute). Based on these results, what is the probability of a boy born to a couple using MicroSort’s YSORT method? Does it appear that the technique is effective in increasing the likelihood that a baby will be a boy?
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