Normal Probabilities

6.2:  Standard Normal Distribution (mean is 0 standard deviation is 1).  For a randomly selected subject, find the probability of a score between 1.37 and 2.42.

• 0.078
• 0.785
• 0.223
• 0.023

6.5 CLT:  Red blood cell counts of women are normally distributed with a mean of 4.577 and a standard deviation of 0.382.  Find the probability that one randomly selected woman has a red blood cell count above 5.4.

• 0.150
• 0.0156
• 0.215
• 0.0237

6.5 CLT:  Red blood cell counts of women are normally distributed with a mean of 4.577 and a standard deviation of 0.382.  What percentage of women have red blood cell counts in the normal range from 4.2 to 5.4?

• 82.3%
• 77.8%
• 72.6%
• 68%

6.3 z-scores: Scores on a history test have an average of 80 with a standard deviation of 6. What is the z-score for a student who earned a 75 on the test?  (Use the formula solve for z)

• -0.83
• 0.83
• -0.17
• 0.17

The scores for the mathematics portion of standardized test are normally distributed with a mean of 541 points and standard deviation of 117 points.

What is the probability that a randomly selected student has a score of 631 points or less on the test?

• 0.1587

• 0.6843

• 0.7791

• 0.3015

The Atlanta hamburger company buys their beef from a farm who reports that their mean weight of Angus steers is 1160 pounds. Suppose that the weight of the animals follow a Normal model with a standard deviation of 83 pounds.

What is the probability of selecting a cow at random that weighs more than 1100 pounds?

• 23.6%

• 76.4%

• 97.3%

• 99.6%

The Atlanta hamburger company buys their beef from a farm who reports that their mean weight of Angus steers is 1160 pounds. Suppose that the weight of the animals follow a Normal model with a standard deviation of 83 pounds.

What is the probability of selecting a cow at random that weighs between 1000 pounds and 1250 pounds?

• 97.3%

• 2.7%

• 83.4%

• 99.4%

A test in your Probability and Statistics class has a mean of 71 and a standard deviation of 3.

If a passing score is 65, what is the probability of passing this test.

• 95%

• 84%

• 97.7%

• 65%

The shelf life of a particular dairy product is normally distributed with a mean of 12 days and a standard deviation of 3 days.

About what percent of the products last between 12 and 15 days?

• 68%
• 34%
• 16%
• 2.5%