This is a binominal distribution -- either the car has problems or it doesnt.
With n=128, the expected mean number with problems is .14*128=17.92 The standard deviation is sqrt(p*q*n) = sqrt(.14*.86*128) = 3.9
.18*128=23.04, which is 5.12 above the mean or 5.12/3.9=1.31 standard deviations away from the mean.
Take it from here....
It is generally believed that electrical problems affect about 14% of new cars. An automobile mechanic conducts diagnostic tests on 128 new cars on the lot.
a. Describe the sampling distribution for sample proportion by naming the model and telling its mean and standard deviation. Justify your answer.
b. What is the probability that in this group over 18% of the new cars will be found to have electrical problems?
1 answer
2 answers