Hi,

Note: The probability of x successes in n trials is: 

P = nCx*  where p and q are the probabilities of success and failure respectively. 

In this case p(CO test) = .8  & q = .2

nCx = 

P(exactly 5 test) = 12C5(.8)^5(.2)^7 = 792(.8)^5(.2)^7 = .0033

P(at least half) = 1 - P(0)-P(1)-P(2)-P(3)-P(4)-P(5)= .9961

Recommend the use of a personal statistical calculator or using the calculators on sites such as: stattrek.com  

RELATED QUESTIONS

 among com[anies doing highway or brige construction , 80% test employees for substance... (answered by stanbon)

7.   Among companies doing highway or bridge construction, 80% test employees for... (answered by stanbon)

For every lot of a liquid substance that arrives, I do a pass/fail test.  I've received... (answered by solver91311)

The yearly rates of traffic accidents and violations were studied for a group of 140... (answered by Boreal)

The yearly rates of traffic accidents and violations were studied for a group of 140... (answered by CPhill)

According to a recent study, 1 in every 6 women has been a victim of domestic abuse at... (answered by jim_thompson5910)

According to a recent study, 1 in every 7 women has been a victim of domestic abuse at... (answered by Boreal)

 The number of cars arrived at toll plaza in any given hour is a random

variable... (answered by reviewermath)

A recent Wall Street Journal article indicated that 38% of American teenagers use... (answered by Boreal)