Multiple choice problems based on Standard normal distribution.

1) At a computer manufacturing company the real size of computer chips is normally distributed with a mean of 1 centimetre as well as a standard deviation of 0.1 centimetre. A random ex of 12 computer chips is taken. describe what is the standard error for the sample mean?

1) 0.029

2) 0.050

3) 0.091

4) 0.120

2) At a computer manufacturing company and the actual size of computer chips is usually distributed with a mean of 1 centimetre and a standard deviation of 0.1 centimetre. A random ex of 12 computer chips is taken. describe the probability that the sample mean will be between 0.99 and 1.01 centimetres?

3) The owner of a fish market has an associate who has determined that the weights of catfish are normally distributed with mean of 3.2 pounds as well as standard deviation of 0.8 pound. If a sample of 25 fish yields a mean of 3.6 pounds what is the Z-score for this observation?

1) 18.750

2) 2.500

3) 1.875

4) 0.750

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

5) Times spent studying by students in the week beforehand final exams follow a normal distribution with standard deviation 8 hours.  A random sample of four students was taken in order to estimate the mean study time for the population of all students. describe the probability that the sample mean exceeds the population mean by more than two hours?