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Anika [276]
3 years ago
12

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

Mathematics
1 answer:
MrMuchimi3 years ago
7 0
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
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The weight of a small Starbucks coffee is a normally distributed random variable with a mean of 330 grams and a standard deviati
just olya [345]

Answer:

Weights of at least 340.1 are in the highest 20%.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the zscore of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

\mu = 330, \sigma = 12

a. Highest 20 percent

At least X

100-20 = 80

So X is the 80th percentile, which is X when Z has a pvalue of 0.8. So X when Z = 0.842.

Z = \frac{X - \mu}{\sigma}

0.842 = \frac{X - 330}{12}

X - 330 = 12*0.842

X = 340.1

Weights of at least 340.1 are in the highest 20%.

3 0
3 years ago
Two times antonio's age plus three times sarah's age equals 34. Sarah's age is also 5 times antonio's age. how old is sarah
Sidana [21]
Sarah's 10 years old.
Antonio's 2 years old.

2 x 2 = 4
10 x 3 = 30
4 + 30 = 34

2 x 5 = 10
4 0
3 years ago
Read 2 more answers
Can somebody please help answer these questions (show ur work)
Ymorist [56]

Answer:

Question 2) 96 Question 3) 246

Step-by-step explanation:

Question 2:
The area of one side of the square is 4x4 which is 16 then you know a cube has 6 sides so 16x6 which is 96.


Question 3:
Well we know the two sides are squares with 3x3 which is 9 and then there are two so 9x2 which is 18

Then the front side with dimensions of 19x3 which is 57 and we know there are 4 sides so we do 57x4 which leads us to 228

Then we add 18 and 228 to find 246

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Orlov [11]
He can have 2 1/3 peoces
6 0
3 years ago
How do you write 169,280 in 4 ways?
storchak [24]

Answer:

Step-by-step explanation:

<u>chcdxjjgccggfztrxcv'.</u>

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<u>asdfghjklkjhgfdsdfgh.</u>

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