B because k is not a specified number
Let X be a discrete binomial random variable.
Let p = 0.267 be the probability that a person does not cover his mouth when sneezing.
Let n = 18 be the number of independent tests.
Let x be the number of successes.
So, the probability that the 18 individuals, 8 do not cover their mouth after sneezing will be:
a) P (X = 8) = 18! / (8! * 10!) * ((0.267) ^ 8) * ((1-0.267) ^ (18-8)).
P (X = 8) = 0.0506.
b) The probability that between 18 individuals observed at random less than 6 does not cover their mouth is:
P (X = 5) + P (X = 4) + P (X = 3) + P (X = 2) + P (X = 1) + P (X = 0) = 0.6571.
c) If it was surprising, according to the previous calculation, the probability that less than 6 people out of 18 do not cover their mouths is 66%. Which means it's less likely that more than half of people will not cover their mouths when they sneeze.
Let's see what the options look like when we multiply the expressions in brackets:
(first, i multiply both parts of the second bracked by the first part of the first bracket, and then the same with the second part of the first bracket:
<span>(1) (3x - 3)(x - 2))
3x2 +6x -3x +6// this is not correct
(2) (3x + 3)(x - 2) </span>
3x2-6x+3x-6//this is not correct
(3)
3(x + 1)(x - 2)
3(x2-2x+x-2)//simplifying:
3(x2-x-2)//multiplying:
3x2-3x-6)
- so this is not correct either
(4) 3(x - 1)(x - 2)
3(x2-2x - x + 2)
3(x2-3x +2)
3x2-9x +6 - well, here is our winner!
<span>164+56-[3+4+1]=
= 164 + 56 - 8
= 212
Have a nice days...........</span>