Exam 2

Question 1

correlation

Answer 1

measures and describes a relationship between two variables

Question 2

linear vs curvilinear

Answer 2

linear: forms a line
curvilinear: has a curve
* to determine do a scatterplot

Question 3

positive vs negative relationship

Answer 3

positive: has an upward slope, direct (when Y increases X increases)
negative: has a downward slop, inverse (when Y increases X decreases)

Question 4

scatterplot

Answer 4

graph used for correlation that graphs all points in a data

Question 5

correlation coefficient (pearson r)

Answer 5

specific measure of a correlation
from -1 to 1

Question 6

pearson r formula

Answer 6

SP/ sqrt SSxSSy

Question 7

coefficient of determination (r^2)

Answer 7

measures the percentage of variability in one variable which is determined by its relationship with the other variable

Question 8

what is another word for the coefficient of determination?

Answer 8

effectsize

Question 9

what are the ranges of effectsize?

Answer 9

small: r=10 -> r2= 1%
mid: r=30 -> r2= 9%
large: r=50 -> r2= 25%

Question 10

spearman rho (rs)

Answer 10

used for ordinary scaling

Question 11

spearman rho formula

Answer 11

rs= 1- (6 sigma D1^2 / N^3 - N)
where:
D1= Rank B - Rank A * sum should equal 0

Question 12

why does correlation not imply cuasation

Answer 12

we are only observing the relationship between the two variables we are not influencing either of them
* there can always be a third variable that is influencing them

Question 13

pearson r

Answer 13

measures the degree of a straight line
- only for interval and ratio scales

Question 14

define regression

Answer 14

regression focuses on using the relationship for the purpose of PREDICTION
- linear relationship between 2 variables
- paired scores

Question 15

define regression line

Answer 15

we can predict a score of one variable (Y) based on our knowledge of the other (X)

Question 16

Linear regression equation

Answer 16

Y’ = byX + ay
where:
by= SP/SSx
ay= Ybar - by(Xbar)

Question 17

regression constant

Answer 17

that value where the regression line crosses the y-axis
* ay

Question 18

standard error of estimate

Answer 18

tells us how far away, on average, a point will be from the regression line
* for accuracy we want a low value

Question 19

Specify the conditions that must be met to use linear regression

Answer 19

• to determine if the relationship is linear use scatterplot
• random sampling
• can only be used to make predictions within the range
• we are not interested in the individuals who are apart of the group used for linear regression

Question 20

define a random sample

Answer 20

each possible sampled of a given size has an equal chance of being selected

Question 21

why is it important to use random sampling?

Answer 21

decreases error

Question 22

what are the two ways to conduct random sampling?

Answer 22

1. sampling with replacement
2. sampling without replacement

Question 23

sampling WITH replacement

Answer 23

each member of the population selected is returned
- does not change probability

Question 24

sampling WITHOUT replacement

Answer 24

selected member of the population is not returned
- probability WILL change

Question 25

a priori

Answer 25

before hand, based on rationalism

Question 26

a posterior

Answer 26

after the fact, based on empiricism

Question 27

a priori formula

Answer 27

p(A) = # of events classifiable as A / total N of possible events

Question 28

a posterior formula

Answer 28

p(A) = # of times A occurred / total N of possible events

Question 29

what are the three basic points in probability?

Answer 29

1. can be defined in two ways: a priori or a posterior 2. can be a fraction, decimal, or percentage 3. range is from 0 to 1

Question 30

the addition rule

Answer 30

p(A or B) = p(A) + p(B) - p(A and B) * OR = ADDITION !! if mutually exclusive: p(A) + p(B)

Question 31

multiplication rule

Answer 31

INDEPENDENT: p(A and B) = p(A) x p(B) DEPENDENT: p(A and B) = p(A) x p(B|A) Mutually exclusive: p(A and B) = 0

Question 32

mutual exclusive events

Answer 32

A and B CANNOT happen at the SAME time; has to be OR

Question 33

independent

Answer 33

they do NOT influence each other = sampling with repalcement

Question 34

dependent

Answer 34

has an effect of probability = sampling without replacement

Question 35

exhaustive

Answer 35

includes all of the possible events

Question 36

when there are only two events...

Answer 36

we call that P and Q - P + Q = 1

Question 37

Define probability in conjunction with a continuous variable

Answer 37

when using a continuous variable use z-score