Find the mean & St. Dev for each.
Mean
St. Dev
X
8
3
Y
12
4
4x  7
3x  2 y
Find the mean & standard deviation
x
p(x)
4
0.2
7
0.31
12
0.24
15
0.18
18
0.07
BINOMIAL
DISTRIBUTION
FORMULA
Section 6.3A
Binomial Experiment - BINS
• Binary?
• There are two possible outcomes – success and failure
• Independent?
• Trials must be independent
• Number?
• The number of trials must be fixed – out of n….
• Success?
• On each trial the probability of success must be the same
Let E be the event that a person goes out shopping on Black Friday.
Find the probability distribution for a sample of 3 people if the P(E) = .78.
Probability distribution of going shopping on black
Friday for 4 people. P(E) = .78
Let’s Develop the formula!
• If I have 5 people, how many ways can I arrange them?
𝟓∙𝟒∙𝟑∙𝟐∙𝟏
• How many ways can I choose 2 of the 5 who went
shopping on black Friday?
[𝟓 ∙ 𝟒] ∙ 𝟑 ∙ 𝟐 ∙ 𝟏
𝟓!
=
𝟑∙𝟐∙𝟏
𝟓−𝟐 !
• But every set of two is the same (SSNNN = SSNNN)…
𝟓!
𝟑!∙𝟐!
Binomial Distribution
 n  x n x
p( x)    p q
 x
n
n!
n Cx    
 x  (n  x)! x !
where
q  1 p
The survival rate for a risky operation is 80%. What is the
probability that exactly 4 of the next 5 patients survive?
USA today stated that 45% of Americans know somebody
who became addicted to a drug other than alcohol. If we
randomly ask 15 people, what’s the probability that exactly 3
were addicted?
What’s the probability that at least 12 are
addicted?
What the probability that less than 3 are
addicted?
90% of the trees planted by a landscaper will
survive. If 10 trees are planted, what’s the
probability more than eight survive?
The probability that a person will subscribe to Statistics
Monthly is 48%. Find the probability that out of a group of
seven, at least one person subscribes.
There are charts as well – but only for some
probabilities so you need to know the formula.
Homework
• Worksheet