Question

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).

Suppose we randomly select 100 tweets.
(a) What is the expected number of these tweets with no reaction?
(b) What are the variance and standard deviation for the number of these tweets with no reaction?

Answer 1

Expected Number=71

Variance =4959

Standard Deviation= 70.42

Explanation:

Expected Number = E (x) = np

Here p = 0.71 and q= 1- 0.71= 0.29 n= 100

Expected Number = E (x) = np = 0.71*100= 71

b) The Variance and Standard Deviation for the number of these tweets with no reaction

Suppose the number of tweets are hundred then the number of tweets with no reaction would be 71 .

Variance = E(x²) - [E(x)]² = (100)²- (71)²= 10000- 5041= 4959

Standard Deviation= √4959= 70.42