Multiple choice questions based on Standard normal distribution.

1. At a computer manufacturing company, the actual size of computer chips is normally distributed with the mean of 1 centimeter and a standard deviation of 0.1 centimeter. A random sample of 12 computer chips is taken. What is the standard error for the sample mean?

a) 0.029
b) 0.050
c) 0.091
d) 0.120

2. At a computer manufacturing company, the actual size of computer chips is normally distributed with a mean of 1 centimeter and the standard deviation of 0.1 centimeter. A random sample of 12 computer chips is taken. What is the possibility that the sample mean will be between 0.99 and 1.01 centimeters?

3. The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.20 pounds and standard deviation of 0.80 pound. If a sample of 25 fish yields the mean of 3.6 pounds, what is the Z-score for this observation?

a) 18.750
b) 2.500
c) 1.875
d) 0.750

4. The amount of time required for an oil and filter change on an automobile is normally distributed with a mean of 45 minutes and a standard deviation of 10 minutes. A random sample of 16 cars is selected. What is the probability that sample mean is between 45 and 52 minutes?

5. Times spent studying by students in the week before final exams follow a normal distribution with standard deviation 8 hours. A random sample of 4 students was taken in order to estimate the mean study time for the population of all students. What is the probability that the sample mean exceeds the population mean by over 2 hours?