Khan Academy on a Stick
Probability and combinatorics
Permutations and combinations. Using combinatorics to solve questions in probability.
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Permutations
ccIntroduction to permutations
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Combinations
ccIntroduction to combinations
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Example: Ways to arrange colors
ccThinking about how many ways you can pick four colors from a group of 6
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Example: 9 card hands
ccThinking about how many ways we can construct a hand of 9 cards
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Example: Ways to pick officers
ccHow many ways can we pick officers for our organization?
Permutations and combinations
You want to display your Chuck Norris dolls on your desk at school and there is only room for five of them. Unfortunately, you own 50. How many ways can you pick the dolls and arrange them on your desk? What if you don't care what order they are in or how they are posed (okay, of course you care about their awesome poses)?
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Example: Probability through counting outcomes
ccThe probability of getting exactly 2 heads when flipping three coins. Thinking about this by visualy depicting all of the outcomes.
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Example: All the ways you can flip a coin
ccManually going through the combinatorics to determine the probability of an event occuring
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Getting Exactly Two Heads (Combinatorics)
ccA different way to think about the probability of getting 2 heads in 4 flips
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Probability and Combinations (part 2)
ccMaking at least 3 out of 5 free throws.
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Probability using Combinations
ccProbability of getting exactly 3 heads in 8 flips of a fair coin.
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Exactly Three Heads in Five Flips
ccProbability of exactly 3 heads in 5 flips using combinations
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Example: Different ways to pick officers
ccThinking about the different ways we can pick officers in order to find the probability of one situation in particular.
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Example: Combinatorics and probability
ccProbability of getting a set of cards
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Example: Lottery probability
ccWhat is the probability of winning a 4-number lottery?
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Mega Millions Jackpot Probability
ccProbability of winning the Mega Millions jackpot
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Generalizing with Binomial Coefficients (bit advanced)
ccConceptual understanding of where the formula for binomial coefficients come from
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Conditional Probability and Combinations
ccProbability that I picked a fair coin given that I flipped 4 out of 6 heads.
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Conditional Probability (Bayes Theorem) Visualized
Conditional probability visualized using trees.
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Birthday Probability Problem
ccThe probability that at least 2 people in a room of 30 share the same birthday.
Probability using combinatorics
This tutorial will apply the permutation and combination tools you learned in the last tutorial to problems of probability. You'll finally learn that there may be better "investments" than poring all your money into the Powerball Lottery.