Ch. 9

Question 0

What is the notation for the correlation coefficient, and what does it describe?

Answer 0

The correlation coefficient = r (Pearson correlation); r = +/- [#]

• The # identifies the strength of the correlational relationship, and can only be a value of 0 - 1.00.
• 1.00 = strongest correlation (high predictability)
• 0.00 = no correlation (very low predictably)
• the +/- = direction of relationship

Question 1

What does the correlational research method examine?

Answer 1

It examines the relationship between naturally-occurring variables.

Question 2

In a study testing anxiety vs. test grade, the correlation coefficient is r=+0.72. Explain what this means.

Answer 2

As anxiety scores increase so too does the test grade, indicating a strong positive relationship that has strong predictability.

Question 3

What is restriction of range?

Answer 3

Restriction of range is an unwanted occurrence she using correlation research. It occurs when only a narrow range of scores is used for one or both variables, and this misrepresents the correlation, so you need a wide range of scores.

Question 4

What is an “outlier”?

Answer 4

An outlier is an extremely different plotted score from others, and it can seriously distort the correlation coefficient.

Question 5

What is regression, and what does it locate?

Answer 5

Regression analysis allows us to make predications based on correlational research. Regression analysis locates the line of best fit.

Question 6

What is the formula for the regression line?

Answer 6

Y=a + bX
a= the place where the line crosses the Y-axis
b= the slope, the lines steepness
- the value of b can be calculated knowing (1) the size of the correlation; (2) the standard deviations for the variables being correlated
- the value of a can be calculated knowing (1) the calculated value of a; (2) the mean scores for the variables being correlated.

Question 7

What is the criterion variable?

Answer 7

The Y in regression line formula.

Question 8

What is the predictor variable?

Answer 8

The X in regression line formula.

Question 9

What is coefficient of determination?

Answer 9

The formula for coefficient of determination is r^2, and it measures the proportion of variability in one variable that can be determined from its relationship with the other variable.

Question 10

What are the two problems that disallow the assumption of casual relationships?

Answer 10

1. ) Directionality problem

2. ) Third Variable Problem

Question 11

What is the third variable problem?

Answer 11

This refers to drawing casual conclusions with correlations. Third variables are any uncontrolled factor that could underlie a correlation between x and y.

Question 12

What is partial correlation?

Answer 12

Partial correlation is a multi variant technique for measuring the effects of a third variable, if the correlation between x and y remains high, a third variable is partialled out; then, it can be eliminated as a third variable.

Question 13

What are intraclass correlation?

Answer 13

Intraclass correlations are a type of correlation that’s used when pairs of scores don’t come from the same person.