Anyone here good with probability mathematics?

I am really not good with this probability stuff. It's not your average problems. It is precalc level, and if anyone can help me out in understanding this please pm me or post here. One of the examples involves making a tree diagram and I am so lost right now. I read the whole chapter (

Give an example.

The numbers 1,2,3, and 4 are written on a seperate slips of paper and placed in a hat. Two slips of paper are then randomly drawn, one after the other and without replacement.

A. Make a tree diagram showing the 12 possibile outcomes of this experiment.

B. Find the probability that the sum of the numbers picked is 6 or more.



I have no clue what the heck they mean by the tree diagram thingy.

B is simple enough, so I'll answer that right now. You know you have to draw a 4 no matter what in order to get a sum of at least 6 (with only 2 drawings.) So that probability is .25. The next draw could be either a 2 or a 3, and there are 3 remaining, so .667.

.25li.667 = ~.1667 (1/6)

yeah that part i understand, this tree diagram shit pisses me off.

The tree diagram probably ought to look something like this...

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Beat me to it keith. )

oh i see thanks. Thanks for the help guys, much appreciated. If i run into problems with the last one i got left ill let you know.

this is pretty basic stuff... are you in stats?

I would also imagine the tree diagram would add up, on the bottom row, the totals. That's how I would do the probability as well. Take the total number over 6, and divide that by 12 (the total number of combinations).

[quote7001dd41ed="Admin"]this is pretty basic stuff... are you in stats?[/quote7001dd41ed]


Na honors precalc. This kind of an assignment to see how much we remember about probability. Frankly, I don't remember anything but thanks to you guys it's all coming back to me. D

these 3 baffled me. I looked online for examples like these three but i was out of luck. Can anyone explain how to do these 3?


3 cards are dealt from a standard 52 card shuffled deck. find the probability that either one ore two are aces.


The second one is Three people are randomly chosen. Find the probability of each event.

a All were born on different days of the week.

b At least two people are were born on the same day of the week.


And the last one Suppose the insurance company not only classifies drivers by age, but in the case of drivers under 25 years old, it also notes whether they have had had a drive's education course. One quarter of its policy-holders under 25 have had a driver's education and 5% of these have an accident in a one-year period. Of those under 25 who have not had driver's education, 13% have an accident within a one year period. A 20-year-old woman takes out a policy with this company and within one year she has an accident. What is the probability she did not have a driver's education course?

The insurance company covers 3 groups Group A includes those under 25 years old ( 22% of it's policyholders), Group B includes those 25-39 in age (43%) and group C includes those 40 and over .

I suck at probabilities. I am good at calculus...

[quote66825c60df="Powerbook"]3 cards are dealt from a standard 52 card shuffled deck. find the probability that either one or two are aces.[/quote66825c60df]

Wording sucks on this, so there are a few different answers I see.
But lets assume no replacement, and the aces are the first 2 cards drawn (math works out any order, but it's easier to explain if they're the first ones drawn)

The probability that one and only one card is an ace
4/52li48/51li47/50= 0.0680542986
(4 aces out of 52 cards)li(48 NON aces out of 51 cards left)li(47 NON aces out of 50 cards left)

The probability that two and only two cards are a aces
4/52li3/51li47/50= 0.00425339367
(4 aces out of 52 cards)li(3 aces left out of 51 cards left)li(47 NON aces out of 50 cards left)

To get the probabability that either happened, since they are exclusive, just add them up.


[quote66825c60df]
The second one is Three people are randomly chosen. Find the probability of each event.

a All were born on different days of the week.

b At least two people are were born on the same day of the week.
[/quote66825c60df]

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