Assign #3 - Quant by Quant

Question 1

visually depicts the association between two quantitative variables.

Answer 1

Scatterplot

Question 2

In a scatterplot, which x-axis would the IV go on?

Answer 2

X-axis

Question 3

In a scatterplot, what does it mean if Y gets larger as X gets larger?

Answer 3

The two variables are said to be positively

associated

Question 4

In a scatterplot, what does it mean if Y gets smaller when X gets larger?

Answer 4

The two variables are said to be negatively

associated

Question 5

What shape is the relationship between the two variables the general tendency of the points follows a straight line?

Answer 5

Linear relationship

Question 6

What is the shape of the relationship if the general tendency of the points follows a curvy path?

Answer 6

Curvilinear relationship

Question 7

In a scatterplot, what are the points that deviate strikingly from the overall pattern?

Answer 7

Outliers

Question 8

measures the direction and strength of a linear association between two quantitative variables.

Answer 8

Pearson’s r

Question 9

What does Pearons’s r indicate when positive, negative or 0?

Answer 9

r = positive = association is positive

r = negative = association is negative

r = 0 = no linear association

Question 10

What does the magnitude of Pearson’s r tell us?

Answer 10

Strength of association between two linear quantitative variables

Question 11

What does Pearson’s r = 1 or -1 mean?

Answer 11

Perfect negative/positive association, points lie on straight non-horizontal line

Question 12

Does Pearson’s r distinguish between independent and dependent variables?

Answer 12

No

Question 13

Does Pearson’s r depend on units of measurement?

Answer 13

No

Question 14

Does Pearson’s r describe curvilinear associations?

Answer 14

No

Question 15

Is Pearson’s r resistant to outliers?

Answer 15

No

Question 16

What does a soccerball shaped cloud of points on a scatterplot mean?

Answer 16

No association

Question 17

What does a football-shaped cloud of points on a scatterplot mean?

Answer 17

Moderate association

Question 18

What does a cucumber-shaped cloud of points on a scatterplot mean?

Answer 18

Strong association

Question 19

What are the two hypotheses for a test of significance of Pearson’s r

Answer 19

Ho: r equals 0 in the population

Ha: r does not equal 0 in the population

Question 20

What are the 3 data assumptions for Pearson’s r

Answer 20

1. Both variables are roughly symmetric.
2. The association between the variables is linear.
3. There are no inordinately influential outliers.

Question 21

What can be represented by the equation Y = bX + a

Answer 21

A straight line in a two-dimensional space

Question 22

the line that minimizes the sum of the squared residuals in a scatterplot.

Answer 22

The OLS (ordinary least squares)

Question 23

What does b represent in the OLS regression line equation of Y = bX + a.

Answer 23

The slope of the line

Question 24

What does ‘a’ represent in the OLS regression line equation of Y = bX + a

Answer 24

The y-intercept, the value of Y at which the line crosses the Y axis

Question 25

How do you calculate 'b' in Y = bX + a.

Answer 25

b = r*(standard deviation of Y / standard deviation of X)

Question 26

How do you calculate 'a' in Y = bX + a.

Answer 26

a = mean of Y – b*(mean of X)

Question 27

What is the standardized regression coefficient of b.

Answer 27

Beta

Question 28

What is beta, the standardized regression coefficient of b.

Answer 28

-a mean of 0 and a standard deviation of 1. -represents the change in Y in standard deviations for a one standard deviation change in X.

Question 29

the proportion of total variability in Y that can be attributed to X.

Answer 29

R2, also called the coefficient of determination

Question 30

What are the 2 uses of an OLS regression line?

Answer 30

1. Summarizing the nature of the association between X and Y | 2. Predicting a Y value for any given X value that we are particularly interested in.

Question 31

measures the direction and strength of an association between two quantitative variables.

Answer 31

Spearman’s rho

Question 32

How is Spearman's rho interpreted

Answer 32

sign and magnitude, bounded by | 1 and –1, etc.

Question 33

What shape of association is used for Spearman's rho?

Answer 33

Curvilinear

Question 33

What shape of association is used for Spearman's rho?

Answer 33

Curvilinear

Question 34

How does Spearman's rho compare to Pearson's r?

Answer 34

t is more resistant to outliers than | is Pearson’s r but is not as powerful as Pearson’s r given that some information is thrown away.

Question 35

For a linear association, is it better to use Pearson's r or Spearman's rho?

Answer 35

Pearson's r