CORRELATION ANALYSIS

Question 1

It shows the relationship between 2 quantitative variables in a visual way.

Answer 1

Scatter plot

Question 2

This data refers to data set with 2 variables.

Answer 2

Bivariate data

Question 3

Linear is either ________ or _______.

Answer 3

positive or negative

Question 4

4 Measures of Association

Answer 4

1. Pearson’s Correlation
2. Point Biserial Correlation
3. Spearman’s Rank Order Correlation
4. Chi-Square Test of Association

Question 5

Measures the strength and direction of the linear relationship between 2 quantitative variables.

Answer 5

Pearson’s Correlation, r

Question 6

Possible values of Pearson’s Correlation are always between ________.

Answer 6

+1 and -1

Question 7

Magnitude of Pearson’s Correlation

Answer 7

0 to 0.2 very weak

0. 2 to 0.4 weak
1. 4 to 0.6 moderate
2. 6 to 0.8 strong
3. 8 to 1.0 very strong

Question 8

True or False. In a Pearson’s Correlation, the value of the correlation coefficient does not depend on which of the 2 variables will be assigned as X and Y.

Answer 8

True

Question 9

True or False. In a Pearson’s Correlation, the absolute value of the coefficient will not change if the units of measurements are changed.

Answer 9

True

Question 10

True or False. Always use Pearson’s Correlation analysis even if the relationship is explained better by a different curve or pattern that is not linear.

Answer 10

False. DO NOT USE Pearson’s Correlation analysis if the relationship is explained better by a different curve or pattern that is not linear.

Question 11

True or False. An observed relationship between 2 variables doesn’t automatically imply that there is some cause and effect relationship between the 2 variables.

Answer 11

True

Question 12

Assumptions of Pearson’s Correlation

Answer 12

• The 2 variables must be at the interval or ratio level.
• There is linear relationship between 2 variables (use scatterplot).
• There should be no outliers.
• The variables should be approximately normally distributed.

Question 13

Measures the strength and direction of the relationship between 1 continuous variable and 1 dichotomous (without natural ordering) variable.

Answer 13

Point Biserial Correlation, r↓pb

Question 14

Assumptions of Point Biserial Correlation

Answer 14

• 1 variable must be continuous and the other is binary or dichotomous.
• There should be no outliers.
• The continuous variable is approximately normally distributed for each category of the dichotomous variable.
• The continuous variable has equal variances for each category of the dichotomous variable.

Question 15

Measures the strength and direction of the monotonic relationship between 2 ranked variables.

Answer 15

Spearman’s Rank-Order Correlation, r↓s

Question 16

What is the relationship called if one of these are true?

• As the value of one variable increases, so does the value of the other variable; or
• As the value of one variable increases, the other variable value decreases.

Answer 16

Monotonic relationship

Question 17

Advantages of p↓s:

Answer 17

• Does not assume that the underlying relationship between X and Y is linear.
• No assumptions of normality are made regarding the distributions of X and Y.
• Variables measured in at least ordinal scale.

Question 18

Aka Pearson’s Chi-square Test or the Chi-square Test for independence.

Answer 18

Chi-square Test of Association

Question 19

Used to determine if a significant relationship exists between 2 categorical variables from a single population.

Answer 19

Chi-square Test of Association

Question 20

Assumptions of Chi-square Test of Association

Answer 20

1. 2 categorical variables
2. 2 or more categories (groups) for each variables
3. Independence of observations
   a. No relationship between subjects in each category.
   b. The categorical variables are not paired in any way (ex: pretest and posttest observations)
4. Data is in the form of observed frequency counts.
5. Relatively large sample size
   a. For 2x2 contingency table
   i. All expected frequencies should be at least 5
   b. For larger tables
   i. Expected frequencies for each cell are at least 1
   ii. Expected frequencies should be at least 5 for the majority (80%) of the cells