Binomial Probability
• Sixty percent of all computer monitors
sold by a large computer retailer have a
flat panel display and 40% have a CRT
display. The type of monitor purchased
by each of the next 12 customers will
be noted. Find the probability that
exactly 6 will purchase a flat panel
display.
• Define what a success is.
• What is the probability of a success?
Binompdf(12,.6,6)=0.1766
• Sixty percent of all computer monitors
sold by a large computer retailer have a
flat panel display and 40% have a CRT
display. The type of monitor purchased
by each of the next 12 customers will
be noted. Find the probability that at
most four will purchase a flat panel
display.
Binomcdf(12,.6,4)=0.0573
• Sixty percent of all computer monitors
sold by a large computer retailer have a
flat panel display and 40% have a CRT
display. The type of monitor purchased
by each of the next 12 customers will
be noted. Find the probability that less
than four.
Binomcdf(12,.6,3)=0.0153
• Sixty percent of all computer monitors
sold by a large computer retailer have a
flat panel display and 40% have a CRT
display. The type of monitor purchased
by each of the next 12 customers will
be noted. Find the probability that
between 4 and 7 will purchase flat panel
monitors . (inclusive)
Binomcdf(12,.6,7) - Binomcdf(12,.6,3)=0.5466
• Sixty percent of all computer monitors
sold by a large computer retailer have a
flat panel display and 40% have a CRT
display. The type of monitor purchased
by each of the next 12 customers will
be noted. Find the mean, variance and
standard deviation of the number of
people that purchase flat panel displays.
μ=7.2
σ2=2.9
σ=1.7
• In recent years, homeowners have
become increasingly security conscious.
A Los Angeles Times poll reported that
almost 20% of Southern California
homeowners questioned had installed a
home security system. Suppose that
exactly 20% of all such homeowners
have a system. Consider a random
sample of 20 homeowners, find the
probability that at least 8 have a
security system.
1- Binomcdf(20,.2,7)=0.0321
• Newsweek reported that one-third of
all credit card users pay their bills in
full each month. This figure is, of
course, an average across different
cards and issuers. Suppose that 30% of
all individuals holding Visa cards issued
by a certain bank pay in full each month.
A random sample of 25 cardholders is
to be selected. Find the mean, variance,
and standard deviation of the number of
cardholders that pay their bills in full
each month.
μ=7.5
σ2=5.3
σ=2.3
Suppose that in a certain metropolitan
area 9 out of 10 households have a VCR.
Calculate the probability that in a group
of four households, exactly two would
have a VCR.
Binompdf(4,.9,2)=0.0486
Suppose that in a certain metropolitan
area 9 out of 10 households have a VCR.
Calculate the probability that in a group
of four households all four would have a
VCR.
Binompdf(4,.9,4)=0.6561
According to a Los Angeles Times survey,
the activity preferred by 80% of airline
passengers on flights is sleeping. If 50
airline passengers are interviewed, find
the probability that 45 prefer sleeping.
Binompdf(50,.8,45)=0.0295
According to a Los Angeles Times survey,
the activity preferred by 80% of airline
passengers on flights is sleeping. If 50
airline passengers are interviewed, find
the mean, variance, and standard
deviation of the number that prefer
sleeping.
μ=40
σ2=8
σ=2.8
According to a Los Angeles Times survey,
the activity preferred by 80% of airline
passengers on flights is sleeping. If 50
airline passengers are interviewed, find
the probability that at least 40 prefer
sleeping.
1-Binomcdf(50,.8,39)=0.5836
Twenty-five percent of the customers
entering a grocery store between 5PM
and 7PM use an express checkout.
Consider ten randomly selected
customers, and let x denote the number
among the ten who use the express
checkout.
Binompdf(10,.25,2)=0.2816
Find P(x=2)
What is P(x≤3) Binomcdf(10,.25,3)=0.7759
What is P(x≥4) 1-Binomcdf(10,.25,3)=0.2241