Angelam1502
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probability
- Thread starter Angelam1502
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HallsofIvy
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- Jan 27, 2012
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It's hard to believe you are serious. You were told "About 26% of orthopedic surgeries involves knee problems." Do you not know what that means?Any help would be much appreciated! I don't just want answers I would like an explanation on how to achieve the answer. I can't seem to understand this probability. Again, any help would be amazing! I really need to understand this. Thanks!!!
About 26% of orthopedic surgeries involves knee problems. The following table summarizes data collected from a sample of adults who have knee surgery. (Source:
American Academy of Orthopedic Surgeons).
Age Full Knee Replacement No Knee Replacement
18 - 44 2 9
45 - 64 25 11
65 – 74 43 27
75 – 84 27 14
85 - older 3 2
1) What is the probability that an orthopedic surgical case selected at random involves
knee surgery?
How many people are listed in the 18-44 category? How many of those had full knee replacement? What percentage was that? Do you know how a "percentage" is related to a "probability"?2) What is the probability that a person from ages 18 – 44 who has knee surgery has a
full knee replacement?
Same as (2)!3) What is the probability that a person from 45 – 64 who has knee surgery has a full
knee replacement?
How many total people had knee surgery? How many had full knee surgery? What percentage is that?4) What is the probability that a person who has knee surgery has a full knee
replacement?
Your book undoubtedly showed you how to lay this kind of problem out in tabular format. Add row totals and column totals to the table you have. In other words, expand your table from 2 by 5 to 3 by 6 and fill in the blanks using addition across for rows and addition down for columns.Any help would be much appreciated! I don't just want answers I would like an explanation on how to achieve the answer. I can't seem to understand this probability. Again, any help would be amazing! I really need to understand this. Thanks!!!
About 26% of orthopedic surgeries involves knee problems. The following table summarizes data collected from a sample of adults who have knee surgery. (Source:
American Academy of Orthopedic Surgeons).
Age Full Knee Replacement No Knee Replacement
18 - 44 2 9
45 - 64 25 11
65 – 74 43 27
75 – 84 27 14
85 - older 3 2
1) What is the probability that an orthopedic surgical case selected at random involves
knee surgery?
2) What is the probability that a person from ages 18 – 44 who has knee surgery has a
full knee replacement?
3) What is the probability that a person from 45 – 64 who has knee surgery has a full
knee replacement?
4) What is the probability that a person who has knee surgery has a full knee
replacement?
Those row and column totals give you the size of your samples for various groups. The first row total gives you the size of the sample of 18-44 year olds. Now you can calculate probabilities for any specific group. For example, the number of people sampled with full knee replacements is 100, and 2 of them were under 45. What does the sample say is the probability that of those who have knee replacements they are under 45?
The answer is 2 / 100 or 2%.