Good morning please help me im in desperate need thxs

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

A number line is divided into fifths. How many equal segments are there between the point at zero and the point 4/5?

ella [17]

Answer:

3?

Step-by-step explanation:

A little confused by the question but is it just

1/5 2/5 3/5 4/5

1 2 3 4

so theres 3 in between

7 0

2 years ago

Square ABCD and square EFGH share a common center on a coordinate plane. is parallel to diagonal . Across how many lines of refl

Oduvanchick [21]

Square ABCD and square EFGH will reflect onto themselves across 8 lines of reflection

7 0

2 years ago

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Can someone help please Stickers are sold in packages of 15 sheets. If there are 20 students in the class, how many packages of

MrRa [10]

Answer:

4 packages

Step-by-step explanation:

If there are 20 and stickers are sold in 15 sheets, then you got to work backwards. take the answer and multiply it by the amount of sheets. For example: 4 times 15 is 60, 60 divided by 20 is 3. No leftover numbers.

8 0

2 years ago

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Is 1/2 equivalent to 5/8

kompoz [17]

<span>No.

To check this yourself, you need the denominators to be the same to be able to easily compare the two.

For example, does 5/8 = 40/64?

1. Determine what you would need to do to the denominator in 5/8 to make it 64. (Multiply it by 8)
2. Find what fraction is equal to 1 with a denominator of 8. (8/8)
3. Multiply the fraction 5/8 by the one you just found (8/8), numerator times numerator, denominator times denominator.
4. Compare the answer with the second fraction.

It is important that when you multiply the denominator by any number you multiply the numerator by the same number. This is to preserve the fraction's value. This works because any number divided by itself is equal to 1, AND when you multiply any number by 1 (whether 1 is in the form of 1 or 4/4 or 8/8 or 234/234), the answer is always equal to the original number.

Another way to check would be to simply enter 1/2 into a calculator, write down the answer. Next enter 5/8 into a calculator. If the answers are the same, they are equal.</span><span>
</span>

8 0

2 years ago

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