SAT Math Level 2 - PROBABILITY Flashcards
Probability of a success
number of possible successes / total number of possible outcomes
Event
Particular outcomes
Complement
Refers to all outcomes in which the event doesn’t happen
P(A U B) =
P(A) + P(B) - P(A and B)
Independent Multiplication Rule
P(A and B) = P(A) x P(B)
P(A | B) =
P(A and B) / P(B)
Permutation
Number of ways you can arrange a set of things
Multiplication Principle
If you can do A in a ways, B in b ways, C in c ways, then the number of ways of doing A then B then C = a x b x c
etc. how many ways can letters P Q R S T U can be arranged if 4 of letters are used each time and each letter cannot be used more than once.
- we can fill the first space 6 ways, the 2nd in 5 ways, the 3rd in 4 ways, the 4th in 3 ways. so 6 x 5 x 4 x 3 = 360 ways
Combinations
Like a permutation but the order of things is not important
Formula for combinations
n! / (n-r)! x r!
n = Total number of things you are choosing from
r = Number of things you want to select
Useful properties of the Mean
1) If you add or subtract the same number from all the data items, then the mean changes by the same amount
2) If you multiply or divide each data by the same number, then the mean is multiplied or divided by the same amount
Standard deviation
How spread out the data is
Small standard deviation
Data is mostly clustered around the mean
Large standard deviation
Data is mostly spread out, far from the mean
Useful properties of Standard Deviation
1) If you add or subtract the same number from all the data items, then the standard deviation is unchanged
2) If you multiply or divide each data item by the same number, then the standard deviation is multiplied or divided the same way
