standard_description: Find the conditional probability of A given B as the fraction of B’s outcomes that also belong to A, and interpret the answer in terms of the model.
problem_activity: Task
In order to play a popular “spinning wheel” game at Fred's Fun Factory Arcade, a player is required to pay a small, fixed amount of 25 cents each time he/she wants to make the wheel spin. When the wheel stops, the player is awarded tickets based on where the wheel stops -- and these tickets are then redeemable for prizes at a redemption center within the arcade.
This particular game has no skill component; each spin of the wheel is a random event, and the results from each spin of the wheel are independent of the results of previous spins.
The wheel awards tickets with the following probabilities:
{"table": [{"_attributes": {"class": ["narrow"]}, "tbody": [{"tr": [{"td": [{"_value": "1 ticket"}, {"_value": "35%"}]}, {"td": [{"_value": "2 tickets"}, {"_value": "20%"}]}, {"td": [{"_value": "3 tickets"}, {"_value": "20%"}]}, {"td": [{"_value": "5 tickets"}, {"_value": "10%"}]}, {"td": [{"_value": "10 tickets"}, {"_value": "10%"}]}, {"td": [{"_value": "25 tickets"}, {"_value": "4%"}]}, {"td": [{"_value": "100 tickets"}, {"_value": "1%"}]}]}]}]}
A young girl is given 2 quarters so that she can play the game two times.  Let $X$ be the number of tickets she wins based on two spins. There are 26 possible values for $X$ that the young girl can obtain in this case, and those values are listed to the right.
Some values of $X$ are more common than others. For example, winning only 2 tickets in two spins is a somewhat common occurrence with probability 0.1225 as it means the player earns 1 ticket on the first spin and 1 ticket on the second spin. Similarly, winning 200 tickets in two spins is a somewhat rare occurrence with probability 0.0001 as it means the player earns 100 tickets on the first spin and 100 tickets on the second spin. A full list of the possible values of $X$ and the corresponding probabilities for almost every value of $X$ is shown at right.
Four probability values are deliberately hidden. Determine the 4 missing probability values in the distribution.  (Hint: since all values of $X$ are listed, and since the probabilities that are shown add up to 0.66, the 4 hidden probabilities you are computing should add up to very specific value.)
Which value of $X$ is most common?
The young girl considers it a "good day" with the game if she wins more than 100 tickets based on 2 spins.  What is the probability that she will have a "good day" based on that definition?
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