Pick 1 pls... im not trynna be mean but pls dont put an answer up here if u dont know

Find the mean, variance &a standard deviation of the binomial distribution with the given values of n and p.

MrMuchimi

A random variable following a binomial distribution over $n$ trials with success probability $p$ has PMF

$f_X(x)=\dbinom nxp^x(1-p)^{n-x}$

Because it's a proper probability distribution, you know that the sum of all the probabilities over the distribution's support must be 1, i.e.

$\displaystyle\sum_xf_X(x)=\sum_{x=0}^n\binom nxp^x(1-p)^{n-x}=1$

The mean is given by the expected value of the distribution,

$\mathbb E(X)=\displaystyle\sum_xf_X(x)=\sum_{x=0}^nx\binom nxp^x(1-p)^{n-x}$
$\mathbb E(X)=\displaystyle\sum_{x=1}^nx\frac{n!}{x!(n-x)!}p^x(1-p)^{n-x}$
$\mathbb E(X)=\displaystyle\sum_{x=1}^n\frac{n!}{(x-1)!(n-x)!}p^x(1-p)^{n-x}$
$\mathbb E(X)=\displaystyle np\sum_{x=1}^n\frac{(n-1)!}{(x-1)!((n-1)-(x-1))!}p^{x-1}(1-p)^{(n-1)-(x-1)}$
$\mathbb E(X)=\displaystyle np\sum_{x=0}^n\frac{(n-1)!}{x!((n-1)-x)!}p^x(1-p)^{(n-1)-x}$
$\mathbb E(X)=\displaystyle np\sum_{x=0}^n\binom{n-1}xp^x(1-p)^{(n-1)-x}$
$\mathbb E(X)=\displaystyle np\sum_{x=0}^{n-1}\binom{n-1}xp^x(1-p)^{(n-1)-x}$

The remaining sum has a summand which is the PMF of yet another binomial distribution with $n-1$ trials and the same success probability, so the sum is 1 and you're left with

$\mathbb E(x)=np=126\times0.27=34.02$

You can similarly derive the variance by computing $\mathbb V(X)=\mathbb E(X^2)-\mathbb E(X)^2$ , but I'll leave that as an exercise for you. You would find that $\mathbb V(X)=np(1-p)$ , so the variance here would be

$\mathbb V(X)=125\times0.27\times0.73=24.8346$

The standard deviation is just the square root of the variance, which is

$\sqrt{\mathbb V(X)}=\sqrt{24.3846}\approx4.9834$

7 0

3 years ago

PLEASE HELP ITS A QUIZ <br> WILL MARK BRAINLIEST (not if you get it wrong)

Tanya [424]

Answer:

27

Step-by-step explanation:

28+17+17+15=76

76÷4= 19

5 0

2 years ago

Keep getting this wrong please help!!!

photoshop1234 [79]

Answer:

14.13 in³

Step-by-step explanation:

Volume of a ball (sphere) is:

V = ⁴/₃ π r³

Circumference of a ball (circle) is:

C = 2π r

Use the circumference to find the radius.

9.42 in = 2π r

r = 1.50 in

Use the radius to find the volume:

V = ⁴/₃ π (1.50 in)³

V = 14.13 in³

4 0

2 years ago

The diameter of the moon is about 3500 km. Approximate the surface area of the moon using the formula for the surface area of a

Contact [7]

Answer:

$3.8465 *10^7$ square kilometers

Step-by-step explanation:

The surface area of a sphere can be found using the formula $SA=4\pi r^2$ . Since the diameter is 3500 km then its radius is half of this. 3500 divided in two is 1,750 units. Substitute r=1,750.

$SA=4\pi r^2\\SA = 4 \pi (1750)^2\\SA = 4 \pi *3,062,500\\SA =38,465,000$

The surface area of the moon is about 38,465,000 square kilometers. Write this is scientific notation using base. $3.8465 *10^7$

4 0

3 years ago

15. Solve the compound inequality.<br> 5x - 11 < -11 or 4x + 2 > 14

s2008m [1.1K]

Answer:

Step-by-step explanation:

5x −11+11<-11+11

5x<0

5x/5<0/5

x<0

4x+2 -2 >14 -2

4x>12

4x/4>12/4

x>3

there both open not closed

hope this helps

5 0

3 years ago