Respuesta :
Answer:
a) 1/11 (b) 7/22 (c) 5/11 (d) 0 (e) 19/66
Step-by-step explanation:
Given the following :
Number of Blue socks = n(B) = 4
Number of Gray socks = n(G) =5
Number of black socks = n(Bl) = 3
Total number of socks = (4 + 5 + 3) = 12
Probability = ( number of required outcomes / number of total possible outcomes)
Picking 2 socks at random:
A) probability of two blue socks :
Ist pick = p(B) = (4/12) = 1/3
Number of Blue socks left = (4 - 1) =3
Total socks left = 12 - 1 = 11
2nd pick = p(B) = (3/11)
P(2 blue socks) = (1/3 * 3/11) = 3 /33 = 1/11
B) No gray socks :
Number of non - gray socks = (4 + 3) = 7
1st pick = 7/12
After 1st pick non-gray socks left = 6
Total socks left = 11
2nd pick = 6 / 11
P(non-gray) = (7/12 × 6/11) = 42/132 = 7/22
C.) Atleast one black socks = (1 - P(no black))
Number of non-black socks = (4 +5) = 9
1st pick = 9/12 = 3/4
After 1st pick, non-black left = 8, total = 11
2nd pick = 8/11
P(non - black) = (3/4 × 8/11) = 24/44 = 6/11
P(atleast 1 black) = (1 - 6/11) = 5 /11
D.) A green socks
Number of green socks = 0
P(green) = 0
E.) A matching socks :
1) matching black socks :
Ist pick = p(Bl) = (3/12) = 1/4
Number of Black socks left = (3 - 1) =2
Total socks left = 12 - 1 = 11
2nd pick = p(Bl) = (2/11)
P(matching black socks) = (1/4 * 2/11) = 2 /44 = 1/22
11) matching blue socks:
Ist pick = p(B) = (4/12) = 1/3
Number of Blue socks left = (4 - 1) =3
Total socks left = 12 - 1 = 11
2nd pick = p(B) = (3/11)
P(matching blue socks) = (1/3 * 3/11) = 3 /33 = 1/11
111) matching gray socks :
Ist pick = p(B) = (5/12) = 5/12
Number of Blue socks left = (5 - 1) =4
Total socks left = 12 - 1 = 11
2nd pick = p(B) = (4/11)
P(matching gray socks) = (5/12 * 4/11) = 20/132 = 5 /33
Summing the probabilities :
(1/22 + 1/11 + 5/33) = (3 + 6 + 10) / 66 = 19/66
Using the hypergeometric distribution, it is found that there is a:
a) 0.0909 = 9.09% probability that you end up with 2 blue socks.
b) 0.3182 = 31.82% probability that you end up with no gray socks.
c) 0.4545 = 45.45% probability that you end up with at least 1 black sock.
d) 0% probability that you end up with a green sock.
e) 0.2879 = 28.79% probability that you end up with matching socks.
Hypergeometric distribution:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
The parameters are:
- x is the number of successes.
- N is the size of the population.
- n is the size of the sample.
- k is the total number of desired outcomes.
In this problem:
- There is a total of 4 + 5 + 3 = 12 socks, hence [tex]N = 12[/tex].
- 2 are grabbed, hence [tex]n = 2[/tex].
Item a:
- 4 are blue, hence [tex]k = 4[/tex]
The probability is P(X = 2), hence:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 2) = h(2,12,2,4) = \frac{C_{4,2}C_{8,0}}{C_{12,2}} = 0.0909[/tex]
0.0909 = 9.09% probability that you end up with 2 blue socks.
Item b:
- 5 are gray, hence [tex]k = 5[/tex]
The probability is P(X = 0), hence:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 0) = h(0,12,2,5) = \frac{C_{5,0}C_{7,2}}{C_{12,2}} = 0.3182[/tex]
0.3182 = 31.82% probability that you end up with no gray socks.
Item c:
- 3 are black, hence [tex]k = 3[/tex].
The probability is:
[tex]P(X \geq 1) = 1 - P(X = 0)[/tex]
In which
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 0) = h(0,12,2,3) = \frac{C_{3,0}C_{9,2}}{C_{12,2}} = 0.5455[/tex]
[tex]P(X \geq 1) = 1 - P(X = 0) = 1 - 0.5455 = 0.4545[/tex]
0.4545 = 45.45% probability that you end up with at least 1 black sock.
Item d:
There are no green socks, hence 0% probability that you end up with a green sock.
Item e:
- 0.0909 probability of two blue.
- The probability of two gray is P(X = 2) when k = 5.
- The probability of two black is P(X = 2) when k = 3.
Hence, for two gray:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 2) = h(2,12,2,5) = \frac{C_{5,2}C_{7,0}}{C_{12,2}} = 0.1515[/tex]
Then, for two black:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 2) = h(2,12,2,3) = \frac{C_{3,2}C_{9,0}}{C_{12,2}} = 0.0455[/tex]
Then, the probability of matching socks is:
[tex]p = 0.0909 + 0.1515 + 0.0455 = 0.2879[/tex]
0.2879 = 28.79% probability that you end up with matching socks.
A similar problem is given at https://brainly.com/question/24826394
