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STatiana [176]
3 years ago
7

What is the formula for the expected number of successes in a binomial experiment with n trials and probability of success​ p? C

hoose the correct forumla below.
A. Upper E (Upper X )equalsStartRoot np (1 minus p )EndRoot

B. Upper E (Upper X )equalsp Superscript n

C. Upper E (Upper X )equals (1 minus p )Superscript n(1 minus p )Superscript n

D. Upper E (Upper X )equalsnp
Mathematics
1 answer:
charle [14.2K]3 years ago
5 0

Answer:

(D)E[ X ] =np.

Step-by-step explanation:

Given a binomial experiment with n trials and probability of success​ p,

f(x)=\left(\begin{array}{c}n\\k\end{array}\right)p^x(1-p)^{n-x}, 0\leq  x\leq n

E(X)=\sum_{x=0}^{n}xf(x)= \sum_{x=0}^{n}x\left(\begin{array}{c}n\\k\end{array}\right)p^x(1-p)^{n-x}

Since each term of the summation is multiplied by x, the value of the term corresponding to x = 0 will be 0. Therefore the expected value becomes:

E(X)=\sum_{x=1}^{n}x\left(\begin{array}{c}n\\x\end{array}\right)p^x(1-p)^{n-x}

Now,

x\left(\begin{array}{c}n\\x\end{array}\right)= \frac{xn!}{x!(n-x)!}=\frac{n!}{(x-)!(n-x)!}=\frac{n(n-1)!}{(x-1)!((n-1)-(x-1))!}=n\left(\begin{array}{c}n-1\\x-1\end{array}\right)

Substituting,

E(X)=\sum_{x=1}^{n}n\left(\begin{array}{c}n-1\\x-1\end{array}\right)p^x(1-p)^{n-x}

Factoring out the n and one p from the above expression:

E(X)=np\sum_{x=1}^{n}n\left(\begin{array}{c}n-1\\x-1\end{array}\right)p^{x-1}(1-p)^{(n-1)-(x-1)}

Representing k=x-1 in the above gives us:

E(X)=np\sum_{k=0}^{n}n\left(\begin{array}{c}n-1\\k\end{array}\right)p^{k}(1-p)^{(n-1)-k}

This can then be written by the Binomial Formula as:

E[ X ] = (np) (p +(1 - p))^{n -1 }= np.

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Answer:

B. Up

Step-by-step explanation:

If you alter a function by adding or subtracting a constant to the end of the expression, then the graph will slide up (down if subtracting) If you alter the x value by altering the expression in close to the x with addition or subtraction the graph will slide left or right.

Vertical translations (sliding up or down) go up when adding and down when subtracting as you would expect it to.

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The answer to your question is UP.

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2 years ago
A shortage of gold causes the price of gold wire to increase by 140%. If 10 feet of gold wire previously cost $50, what is the n
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