# Probability using standard normal distribution

1. The mean amount of gasoline and services charged by Key Refining Company credit customers is $70 per month. The distribution of amounts spent is approximately normal with a standard deviation of $10. What is the probability of selecting a credit card customer at random and finding the customer charged between $70 and $83?

A) 0.1962

B) 0.4032

C) 0.3413

D) 0.4750

2. The upper and lower limits of a uniform probability distribution are:

positive and negative infinity.

plus and minus three standard deviations.

0 and 1.

the maximum and minimum values of the random variable.

11. The employees of Cartwright Manufacturing are awarded efficiency ratings. The distribution of the ratings approximates a normal distribution. The mean is 400, the standard deviation 50. What is the area under the normal curve between 400 and 482?

A) 0.5000

B) 0.4495

C) 0.3413

D) 0.4750

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#### Solution Summary

This solution is comprised of a detailed explanation of standard normal distribution or z score. In this solution, step-by-step explanation of this complicated topic provides students with a clear perspective of standard normal distribution to find the probability.