# Random variable modeling arthroscopic meniscal repair

The below problem is from my introductory stats textbook, the chapter on random variables and probability distributions. I don't even know what's being asked, much less how to answer it. Any clues?

   Arthroscopic meniscal repair was successful 70% of
the time for tears greater than 25 millimeters (in 50 surgeries)
and 76% of the time for shorter tears (in 100 surgeries).
(a) Describe the random variable used in these probability
statements.
(b) Is the random variable continuous or discrete?
(c) Explain why these probabilities do not add to 1.


So I've gone with (a) Binomial random variable (b) Discrete, because its binomial (c) They don't add to one as each is measuring the probability of a different thing.

I just want to make sure I'm not completely off-track here.

• You might get a little more help if you show a little bit more effort (like what you've tried so far, etc)... – barak manos Sep 9 '14 at 13:18
• (a) and (b) are just a question of learning the jargon. You have the book, look them up. What about (c)? Have you tried to do that? – almagest Sep 9 '14 at 13:34
• @almagest I wasn't sure with (a) if it was asking me to define a function or just describe which part of the question was the variable. Am I right in thinking that the variable is success/failure (binomial) And for (c) I'm assuming they don't add to 1 because they are two separate variables – user3544027 Sep 9 '14 at 13:42
• The second. Your textbook has a particular way of approaching this kind of problem and it wants to make sure you have understood the definitions it uses ie do you know what a random variable is? – almagest Sep 9 '14 at 13:44
• I think that last comment is the sort of thing people are looking for in a question. You can edit the question to include those thoughts. – David K Sep 9 '14 at 13:47