Normal Distribution, Z-Score

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%

μ = 70 , σ = 8 , X = 50 . Find z score

• 2.5

• -2.5

• 5.2

• -5.2

This data is normally distributed.  What percent of the data is in the shaded region?

• 68%

• 95%

• 99.7%

• 50%

Adam's Z-score on a test is +2.50. What does this mean?

• Adam's score has a 2.5% chance of being better than any other randomly selected score.

• Adam's test score was better than 25% of his peers.

• He scored 2.5 standard deviations above the average.

• He did terrible.

The # of standard deviations an observation falls from the center of a Normal distribution.

• Z-score

• t-score

• Standard Error

• Percentile

In a normal distribution, the z-score for the mean is 0.

• True

• False

The weights of laboratory cockroaches follow a Normal distribution with mean 80 grams and standard deviation 2 grams. The following figure is the Normal curve for this distribution of weights.
Point C on this Normal curve corresponds to

• 84 grams.

• 82 grams.

• 78 grams.

• 76 grams.

• 74 grams.

The heights of students in a class follow a normal distribution with a mean of 65 inches and a standard deviation of 3 inches. John is 70 inches tall, while Sarah is 67 inches tall. Calculate the z-scores for John and Sarah and determine who is taller than their peers.

• John is relatively taller than Sarah.

• Sarah is relatively taller than John.

• John and Sarah are equally tall.

• insufficient information to determine who is relatively taller.

In this formula, the y is one of the cut points in a Normal curve.

• True

• False

Joanne's Z-score is -1.5. What does this mean?

• She didn't take the test yet.

• She scored 1.5 standard deviations below the average.

• She did better than most people.

• No clue