PLS HELP ITS EMERGENCY
1 answer:
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Answer:
a) E(X) = 71
b) V(X) = 20.59
Sigma = 4.538
Step-by-step explanation:
<em>The question is incomplete:</em>
<em>According to a 2010 study conducted by the Toronto-based social media analytics firm Sysomos, 71% of all tweets get no reaction. That is, these are tweets that are not replied to or retweeted (Sysomos website, January 5, 2015). </em>
<em> Suppose we randomly select 100 tweets. </em>
<em>a) What is the expected number of these tweets with no reaction? </em>
<em>b) What are the variance and standard deviation for the number of these tweets with no reaction?</em>
This can be modeled with the binomial distribution, with sample size n=100 and p=0.71, as the probability of no reaction for each individual tweet.
The expected number of these tweets with no reaction can be calcualted as the mean of the binomial random variable with these parameters:
The variance for the number of these tweets with no reaction can be calculated as the variance of the binomial distribution:
Then, the standard deviation becomes:
Since the first part says the value is five less then twice the square of a negative number we get the first equation as 2(-x)²-5. Then we have that -9x is equal to that previous equation. Therefore our new equation is 2(-x)²-5=-9x. We can move the nine over by adding it to both side to get 2(-x)²+9x-5=0. Then you can use any method of factoring (I prefer quadratic formula) to get your values for x. By doing so, you’ll get x=28 and x=-32.5. Since the problem said the number was negative in the first part, you know you can’t have the 28 as the answer so the right answer is -32.5.
Answer:
p = -0.004n+34
Step-by-step explanation:
The slope of the linear equation can be found by using the two given points (30, 1000) and (22, 3000):
Applying the point (30, 1000) to the general form of a linear equation with m =-0.004, gives us the linear relationship between price (p) and number of shirts (n):