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# Probability homework question ??

markr

1
Thu 3 May, 2012 01:48 pm
@mihanni21 ,
a4 is wrong. How many education majors did they list?

b1 is wrong. What's the probability of picking a man with one pick (how many men are there? how many people are there)? Now that you've removed one man from the general population, what is the probability of picking another man (hint: the numbers used to calculate the probability for the first man have changed)? Now that you have two probabilities, what do you do with them? Hint: You want a man AND a man. See earlier post about and/or.

b2 is wrong. This is a little trickier. Just using probability, what you want is P(selecting a bio then a ling) OR P(selecting a ling then a bio)

Using combinatorics (counting techniques), you want the number of bio/ling pairs divided by the total number of pairs. That would be (50*25) / C(200,2) where C(200,2) means the number of combinations of 200 items selected 2 at a time.
markr

1
Thu 3 May, 2012 01:59 pm
@mihanni21 ,
b3 - How many male chem majors are there? They don't say, but you know how many chem majors there are, and you know the ratio of men to women. Likewise for the female bio major. Now that you "know" how many there are of each, how many ways can you select a pair of them (# of male chem * # female bio). Divide that by the total number of pairs (you already calculated this in b2).

c1 requires a different approach. The probabilities of all possible outcomes sums to 1. So, P(0 are ling) + P(1 is ling) + P(2 are ling) + P(all 3 are ling) = 1. You want P(1 is ling) + P(2 are ling) + P(all 3 are ling). Well, that equals 1 - P(0 are ling). Figure out the probability of none of them being linguistics majors, and it's easy to answer the question. This gets back to combinatorics. How many ways can you pick three people such that none of them are linguistics majors? Hint: Remove all of the linguistics majors from the population and determine how many ways there are to select 3 people. Now, put them back, and determine how many ways there are to select 3 people from the total population. Compute a probability from these numbers.
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markr

1
Thu 3 May, 2012 02:02 pm
@mihanni21 ,
c2 is simpler. First determine the probability of selecting a psych major. Now, with the remaining people, determine the probability of selecting a chem major. Now, with the remaining people, determine the probability of selecting an eng major. You've got three probabilities. Hint: You want a psych AND a chem AND an eng.
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mihanni21

1
Thu 3 May, 2012 02:27 pm
@markr,
Sorry but I still confused>? there are not really any education majors listed, I thought ling was one? but I guess not.

markr

1
Thu 3 May, 2012 03:24 pm
@mihanni21 ,
If there are none, then what is the probability of picking one?
mihanni21

1
Thu 3 May, 2012 05:17 pm
@markr,
none??
markr

1
Thu 3 May, 2012 07:02 pm
@mihanni21 ,
Yes. 0/200
0 Replies

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