Study Guide for problem #11

Craig Shaw

#11=New York State has found that 30% of all consumer complaints are valid. If the State received 6000 complaints last year, about how many of them are expected to be valid? (i.e. find the mean). Find the standard deviation.

Step 1: The first thing you want to do is to find n,p,q. n and p are given in the problem where n is the sample population and p is the probability. you find q by subtracting 1 (represents 100-%) from .3.

n=6000          p= 30%  or  .3        q=1-.3=70%   or  .7

Step 2: Now you can find the mean by using this formula-

mew=n * p

6000 * .3=1800 (valid complaints)

Step 3: Finally we can find the standard deviation by using the formula below.

S.D= (SquareRoot of) n * p * q

(SqRt of ) 6000 * .3 * .7

(SqRt of) 1260