Transcript 6.6 The Mean and Standard Deviation of the Binomial Distribution

Advanced Math Topics
6.6 The Mean and Standard
Deviation of the Binomial
Distribution
The formula for the mean of a binomial distribution, where n = the number of trials
and p = p(success) is…
μ = np
A retail clothes store generally gets a return of 8% of its merchandise. If the store
sells 100,000 items this month, about how many items will be returned? (find the
mean?
μ = np
μ = (100,000)(.08)
μ = 8,000
Approximately 8,000 items will be returned.
The formula for the variance and standard deviation of a binomial distribution,
where n = the number of trials, p = p(success), and q = p(failure) is…
σ2 = npq
σ =√npq
A retail clothes store generally gets a return of 8% of its merchandise.
Last month it sold 100,000 items. Find the standard deviation.
σ =√npq
σ =√(100,000)(.08)(.92)
σ =√7,360
σ = 85.79
The standard deviation is 85.79.
From the HW P. 330
1) A meat packing company found that 38% of its packages weigh at least 2 ounces
less than what was listed on the package. If 600 packages were sold to a local
supermarket, how many can be expected to weigh at least 2 ounces less than its
stated weight? Find the standard deviation.
228 and 11.889 B.O.B. is wrong for #1 in some books
HW
P. 330 #1-12
Anyone can get a staph infection. People are more likely to get one if they have:
Skin-to-skin contact with someone who has a staph infection
Contact with items and surfaces that have staph on them
Openings in their skin such as cuts and scrapes
Crowded living conditions
Poor hygiene
The incidence of staph infections can be greatly decreased by practicing good hygiene
and taking the following measures:
Wash your hands often and use an alcohol-based hand sanitizer
Keep all cuts, scrapes and wounds clean and covered with bandages
Do not touch other people’s cuts or bandages
Do not share personal items such as towels, razors, body jewelry, deodorant or soap that
directly touch the body
Encourage students who participates in contact sports to shower and wash up immediately
after each game or practice
Wash dirty clothes, linens, and towels in hot water and laundry detergent. Use a hot dryer
instead of air drying because the heat also helps kill bacteria
Maintain a clean environment and establish cleaning procedures for frequently touched
surfaces that come into direct contact with people’s skin I love you-cox happy bday