Topic: conditional probability list of topics
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	Conditional probability		2010-03-26
		From Sandy: In a certain school, it is known that 80% of the students use the internet for school projects, 60% use e-mail on a regular basis, and 90% use the internet for school projects or for e-mail on a regular basis. A student from this school is selected at random Determine the probability that the student used e-mail, given that the student used the internet for school projects. Sandy Answered by Penny Nom.
	Conditional probability		2009-06-01
		From Tanja: A biased coin where P(heads) =3/5 is flipped 4 times. What is the probability of getting at least 3 heads given at least 1 heads is flipped? I can calculate this using P(A|B) =P(AandB)/P(B) but I've had students asking me how you would work this question out the "long way" without the formula. I'm am unsure about how you do this the long way. Answered by Robert Dawson.
	Conditional probability		2008-01-14
		From Sara: Hello! Ian has a photocopier in his office. If the photocopier is working on a certain day then the probability that it will be working the next day is 0.9. If the photocopier is not working on a certain day then the probability that it will not be working the next day is 0.3. The photocopier is not working on Monday. (a) Calculate the probability that it will be working on Tuesday and Wednesday. (b) Calculate the probability that it will not be working on Wednesday. Could you please draw a tree diagram for this problem. Answered by Penny Nom.
	The case of the forgotten umbrella		2007-12-25
		From rougi: a lecturer goes to a bar because it looks like raning.he takes an umbrella with him. on the way to bar he forgets the umbrella in the bus with probability 0,1,in the bar with probability 0.3 and on his way home in the taxi with probability 0,6 a)what is probability that he forgets the umbrella on his tripe? b)when he gets home he realizes that he has forgotten his umbrella,what is probability that he has forgotten it in the taxi? Answered by Stephen La Rocque and Harley Weston.
	Undercapatalized small businesses		2004-06-26
		From Greg: Suppose that 30% of all small businesses are undercapitalized. 40% of all undercapitalized small businesses fail and 20% of all small businesses that are not undercapitalized fail. A small business is chosen at random. The probability that the small business succeeds if it is undercapitalized is? Greg Answered by Penny Nom.
	Drawing cards		2002-06-11
		From Ed: What is the probability of drawing without replacement from a standard deck of 52 cards the following 5 card hand ...... the ace of spades, 2 tens and 2 face cards Solution 1: 1/52 x 4/51 x 3/50 x 12/49 x 11/48 Solution 2: Using Combination theory ..... (1C1 x 4C2 x 12C2) divided by (52C5) Can you help us understand which answer is correct and why the other is not? Answered by Penny Nom.
	Conditional probability		2002-05-19
		From Manny: In a certain school, it is known that 80% of the students use the internet for school projects, 60% use e-mail on a regular basis, and 90% use the internet for school projects or for e-mail on a regular basis. a student from this school is selected at random Determine thge probability that the student used e-mail, given that the student used the internet for school projects. ANS: how can i solve this question by useing the vin diaagram Answered by Andrei Volodin.
	An award ceremony		2002-05-13
		From Mika: Five students are equally qualifide their school at an award ceremony. two students will be randomly chosen to go to the ceremony. (a) if Tony is one of the five student, what is the probability that he will be chosen? Ans: 2/5C2=0.2 which is 20% (b)Tony's friend, Allecia, who was also eligible to go, has been chosen. what is the Tony's probability of being chosen after he learns that allecica is going: Ans: 1/5C1=0.2 I think the answes are wrong please help me with these questions Answered by Andrei Volodin.
	Is the tree a pine tree?		2001-10-27
		From Kate: Suppose Stock Brokers tell the truth 2/5 of the time, and 1/3 of the trees in a given forest are Pine. If 4 Stock Brokers say that a certain tree in that forest is Pine, what is the probability that the tree is indeed a Pine tree? Answered by Penny Nom.
	Rolling two dice		2001-09-10
		From Owen: This probability question has been bugging me for a while. Two ordinary dice are rolled. If it is known that one shows a 5, what is the probability that they total 8? I have two different but (seemingly) correct solutions. Answered by Andrei Volodin.
	Conditional probabiity		2001-01-22
		From Wallace Yang: A pair of six-sided fair dice is thrown. Find the probability that the sum is 10 or greater if it is given that a 5 appears on at least one of the dice. Answered by Penny Nom and Claude Tardif.

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