According to a study conducted by the Toronto-based social media analytics firm Sysomos, 75% of all tweets get no reaction. That is, these are tweets that are not replied to or retweeted (Sysomos website, January ). Suppose we randomly select tweets.

a. What is the expected number of these tweets with no reaction (to the nearest whole number)?

b. What are the variance (to 2 decimals) and standard deviation (to 4 decimals) for the number of these tweets with no reaction? Variance Standard deviation

Answer:

The mean is $\mu = 150$

The variance $\sigma^2 =37.5$

The standard deviation is $\sigma \approx 6.1237$

Step-by-step explanation:

A binomial distribution is mathematically represented as $B(n,p)$

where n denotes the number of independent trials =200

And p denote the probability of success = 0.75

We also have the probability of failure which is denoted as q and is equivalent to $1-p$

if p and q are constant then

In binomial distribution the probability of x success and (n-x) is mathematically represented as

$P[X =x] =[\left n} \atop x}} \right. ] p^x (1-p)^{n-x}$

Where x= 0,1,2,...,n $for 0\le p \le 1$

Now $[\left n} \atop x}} \right. ] = \frac{n!}{x(n-x)!}$

Now the mean(Expected number ) of these probability in binomial distribution is mathematically represented as

$\mu = np$

$= 200 *0.75 = 150$

And the variance is mathematically represented as

$\sigma^2 = np(1-p)$

$= 200 * 0.75 (1-0.75) = 37.5$

And the standard deviation is mathematically represented as

$\sigma = \sqrt{np(1-p)}$

$= \sqrt{200 *0.75(1-0.75)} =\sqrt{37.5} \approx 6.1237$

We can obtain the standard z -score of a d

6 0

3 years ago

Ten runners join a race. In how many possible ways can they be arranged as first, second, and third placer? Pls answer

Daniel [21]

Ans: 720

<span>This is equal to the number of different arrangements of three persons from a group of 10 persons </span>

Required number of ways = 10P3 = 720

OR can be solved in this way
select 3 runners (10C3 ways)
These 3 runners can be arranged in 3! ways
<span>Total = 10C3×3! = 720

</span>

5 0

3 years ago

Read 2 more answers

Follow directions please. Do your best. You don't need to explain. I am not doing BRAINLIEST anymore. It causes too many problem

liraira [26]

Answer: 760267200

Step-by-step explanation:

4 0

3 years ago

A middle school took all of its 6th grade students on a field trip to see a play at a theater that has 3700 seats. The students

igomit [66]

Answer:

1,924 6th graders

Step-by-step explanation:

52% of 3700 seats

0.52 x 3700= 1,924 seats filled

8 0

2 years ago