Notesale: Turn your study into money

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PROBABILITY OF GRE
Probability is one of these grab bag Quant areas that we 're going to see occasionally
occasionally
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One of those things you 're reliably see anywhere from two to four
questions on the test
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Probability is always going to be
between 0 and 1
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Uh see how you can do on that and I'll just
put that definition up on the board here successes over total
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5 is my Center here and let 's
just deal with this before we think about other cases what 's the probability that the number
selected is greater than the average
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The average of these middle two numbers and I 'm
giving a lot of like uh stats stuff here that maybe feels unfamiliar if it does that's okay
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What we 've been doing is dealing with the probability of one thing happening
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Once I roll this 24-sided Cube once we pick one number from a set of ten
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Roll one and roll two
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One of the things we need to be looking out for is there multiple success scenarios
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within each scenario
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That distinction can
sometimes be a little confusing
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We 're looking for the probability that we get a heads
and a six so it 's one half times one-sixth which is 1 over 12 and our answer is B good hopefully
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Let 's keep going we 're going to start upping the difficulty a little
bit okay so probability for any given day is 1 6 to have rain
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The threeness of it specifically matters no more than rolling a three on dice, so
as we 're doing these probabilities with multiple events we need to ask ourselves are we dealing
with replacement like rolling dice or flipping coins where the probability is constant
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Let 's try another one again
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We want the probability at least one of the rolls is greater than four so let 's think about the ways
this could happen
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The
probability of each of these individually is going to be 1-6 times 1 6 for 1 over 36
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would be if we see this five success scenarios? We can ask how many total cases and
for that we would need to use combinatorics
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The easier method is to do one minus failure because there are fewer failure
scenarios so that 's all the time we've got for right now
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