Probability Flashcards
P(a|b)
(find % given table)
do that combined number / b column total
P(A|B^c)
(find percent given table)
do all but B in the A column / all but B in the total column
given 2 % numbers find it contains A or B
make ven diagram
P(AUB)
make probability /100
add the numerators
given 2 % numbers, find the probability that it contains A or does not contain B
make ven diagram
P(AUB^c)
numerator of fraction includes the number on the bottom of diagram and middle /100
given 2 percentages
ex- 40% dogs 32% cats 18% both
find the probability that they own A given B
P(A|B)
use formula: P(AandB)/P(A)
independent=
same %
given table
is A and B independent?
do P(A|B) = %
and P(A) = %
P(A)= total A / total
candy box has 20 chocolates. 14 soft, 6 are hard. Find the probability you pick 3 soft candies in a row
14/2013/1912/18
given 3 percent values
ex- a cancer test has sensitivity of 92%, specificity of 89%. assume 4% have cancer
what is the probability you have cancer?
do tree diagram
use formula
ex- P(actually have cancer|positive test)
P(A|B)/P(A)
(the first 2) / (1st)(pos)+(2nd)(pos)
soft candy question the 14/20 * 13/19… but they give you a probability
(probability)^(how many)
soft candy question the 14/20 * 13/19… but they give you a probability
what’s the probability that 1 is wrong
do (probability)^(how many)
then 1- that
given:
P(A)=
P(B)=
P(AnB)=
are A and B independent?
so P(A) times P(B)
if it equals the same as P(AnB) then yes independent
complete the two way table
when A and B are mutually exclusive
they dont occur at the same time so the top left corner is 0
complete the two way table
when A and B are independent
do A/total times B/total
then do that probability times the total
soft candy question the 14/20 * 13/19… but they give you a probability and dont give you how many
what’s the probability that the candy, test, whatever is not right
(1-A) times (1-B)
“the detectives found that 40% of the people with food poisoning went to a cocktail party on the second night of the conference”
do P(whatever)
F=got food poisoning
A= attended party
P(A|F)
probability that they attended the party was 40% given they got food poisoning
given:
P(A)=
P(B)=
what is P(AuB)
do A+B - P(AnB)
P(AnB)=multiply A and B
what can you compare to P(A|B) to see if its independent
P(A) and P(A|B^c)
discrete random variable
YES gaps (NO decimals)
1, 2, 3, 4
continuous random variable
NO gaps (YES decimals)
1, 1.1, 1.2
P(X>=3)
add numerators / total
how to calculate mean
E(x)= X(P%)+X(P%)+x(P%)
how to calculate mean/SD in calculator
stat, edit, 12345 and probability, stat calc edit, L1, L2, calculate
how to describe mean
“If I choose many many ___(ppl, gum)___ , the average number of __(ppl, gum)__ in __fam, pack___ will be ___
