Chapter 5: Probability, Normal Distributions, & Z Scores

Question 1

What is probability (p) ?

Answer 1

Probability is the frequency of times an outcome occurs divided by the total number of possible outcomes.

Question 2

What is a normal distribution?

Answer 2

The normal distribution is a theoretical distribution in which scores are symmetrically distributed above and below the mean, the median, and the mode at the center of the distribution.

Question 3

The mean, median, and mode are all located at what percentile of a normal distribution?

Answer 3

50th percentile

Question 4

The standard deviation is never…

(+/-)

Answer 4

Negative

Question 5

The total area under the curve of a normal distribution is equal to…

Answer 5

1

Question 6

What is the standard normal distribution (z distribution) ?

Answer 6

The standard normal distribution, or z distribution, is a normal distribution with a mean equal to 0 and a standard deviation equal to 1. The standard normal distribution is distributed in z score units along the x- axis.

Question 7

What is the mean of the standard normal distribution?

Answer 7

0

Question 8

What is the standard deviation of the standard normal distribution?

Answer 8

1

Question 9

Why is the standard normal distribution useful?

Answer 9

Because we know the probabilities under a standard normal curve, we can convert all other normal distributions to this standard. By doing so, we can find the probabilities of scores in any normal distribution using probabilities listed for the standard normal distribution.

Question 10

What is a z score?

Answer 10

A z score is a value on the x-axis of a standard normal distributiont that specifies the distance or the number of standard deviations that a value is above or below the mean.