Question

Approximately 15% of Americans have a blood type of B. The local blood bank has 80 donors stop by on a given day (which can be considered a random sample from the population). What is the probability that between 15% and 20% of the donors on a given day have a blood type of B? Be sure to state and justify your assumptions.

Answer 1

@jim_thompson5910

Answer 2

This is one of the other ones I need help with

Answer 3

ok one sec

Answer 4

kk

Answer 5

I think it's a binomial distribution problem, but I'm double checking to make sure

Answer 6

kk

Answer 7

ok I've confirmed it's a binomial distribution problem, here is the calculator we'll use

http://stattrek.com/online-calculator/binomial.aspx

Answer 8

the first two boxes will have these two values

0.15
80

Answer 9

Ok1

Answer 10

I did

Answer 11

the next box will have the value of 16

why 16? because 20% of 80 is 16

this is the right endpoint of the interval

Answer 12

so you'll have

0.15
80
16

hit enter

Answer 13

kk i did

Answer 14

look for: Cumulative Probability: P(X <= 16)

make sure there's a line under the <

Answer 15

it says binomial Probability: P(X = 16) : 0.053822345775557

Answer 16

look for the value next to: Cumulative Probability: P(X <= 16)

Answer 17

0.916288694306713

Answer 18

good, keep this number in mind

Answer 19

kk

Answer 20

now take 15% of 80 to get 0.15*80 = 12

then move to the next integer below that to get 11

now replace the 16 with 11, so you should have

0.15
80
11

hit enter and read off the number next to "Cumulative Probability: P(X <= 11) "

Answer 21

.4522??

Answer 22

0.452190494037699?

Answer 23

good, you rounded, but that's ok

Answer 24

now subtract this from the previous value you got

0.916288694306713-0.452190494037699 = 0.46409820026901

Answer 25

ok

Answer 26

is that the answer?

Answer 27

this is the probability that between 12 and 16 people (both inclusive) will have blood type B

Answer 28

0.916288694306713-0.452190494037699 = 0.46409820026901

Answer 29

12 is 15% of 80
16 is 20% of 80

so the probability that between 15% and 20% of the donors on a given day have a blood type of B is roughly 0.46409820026901

and you can round that however you need to

Answer 30

so the answer:

so the probability that between 15% and 20% of the donors on a given day have a blood type of B is roughly 0.46409820026901

Answer 31

yeah you'll have to show how you got it of course

Answer 32

i only have like one more essay then like multple choice ones, it will only take a litter. ill post it now ! thanks!

Answer 33

basically using this idea

P(k <= X <= m) = P(X <= m) - P(X<= k-1)

for binomial distributions

Answer 34

kk posting my new one