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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

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.