Question
3. (1 5 points) In a 1999 survey of teachers by USA Today revealed that 85% of teachers had years. If 30 teachers are selected at random, find the probability that at least 1 tencher had encountered a student with such a weapon in the last three years. (If you use the Binomial, justify its use.) ( I 5 points) Information from. the Census Bureau tells us that 2S% of American men have a bachelor's degree or higher. If 15 American men are selected at random, find the mean and standard deviation of the resulting binomial probability distribution (x- number of men with a bachelor's degree or higher.)
Explanation / Answer
3.The required probability is P(X>=1)
=1-P(X=0)
=1-30C0*(1-0.85)^0*0.85^30
=1-0.007=0.993
4.The mean is np=15*0.28=4.2
The standard deviation is: sq rt of np(1-p)=sq rt of 4.2*(1-0.28)=1.73