Use the Normal to model the distribution of sample proportions.
-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. What is the
Probability that in this group over 18% of the new cars will be found to have electrical
Problems?
A) 0.0985
B) 0.197
C) 0.9015
D) 0.803
E) 0.500

Question

Quizplus · Accepted Answer

To find the probability that over 18% of the cars have electrical problems, we use the normal approximation to the binomial distribution. The mean (μ) is 0.14 and the standard deviation (σ) is sqrt(0.14*0.86/128). We convert 0.18 to a z-score and find the probability using the standard normal distribution table. The probability is approximately 0.0985.

Use the Normal to Model the Distribution of Sample Proportions