Chapter 6: Probability

Question 1

how is probability determined?

Answer 1

determined by a ratio comparing the frequency of occurrence for that outcome relative to the total number of possible outcomes

Question 2

how is probability expressed?

Answer 2

as a proportion, fraction, or percentage

Question 3

why do we use probability?

Answer 3

to relate the population back to samples

Question 4

what is the most common z-score

Answer 4

0

Question 5

what is the least common z-score

Answer 5

± 3

Question 6

Probability of picking a score within one standard deviation of the mean

Answer 6

0.68

Question 7

Probability of picking a score within two standard deviations of the mean

Answer 7

0.95

Question 8

Probability of picking a score within three standard deviations of the mean

Answer 8

0.997

Question 9

Column A of the unit normal table

Answer 9

lists z-score values.

Question 10

column B of the unit normal table

Answer 10

body of the distribution

Question 11

column C of the unit normal table

Answer 11

tail of the distribution

Question 12

column D of the unit normal table

Answer 12

the proportion between the mean and the z-score location.

Question 13

How do you find the probability corresponding to a particular score? (X)

Answer 13

1. Transform the score into a z-score
2. Look up the z-score in the table and read across the row to find the appropriate proportion/probability

Question 14

How do you find the score corresponding to a particular proportion?

Answer 14

1. Look up the proportion in the table
2. Read across the row to find the
   corresponding z-score
3. Transform the z-score into an X value.

Question 15

The proportions of positive and negative values of a specific z-score

Answer 15

are the same

Question 16

proportions are always ___

Answer 16

positive

Question 17

tail of the distribution of a negative z-score is

Answer 17

on the left

Question 18

tail of the distribution of a positive z-score is

Answer 18

on the right

Question 19

random sampling

Answer 19

each person had an equal chance of being in the sample

Question 20

independent and random sampling

Answer 20

each person in the sample had an equal chance, and once someone is in the sample, it doesn’t influence someone else’s chance of being in the sample

Question 21

are indepedent random samples drawn with replacement?

Answer 21

yes

Question 22

The percentile rank for a score in a normal distribution

Answer 22

the proportion to the left of the score.