### Who is responsible for the invention of the Pearson product-moment correlation coefficient?

Karl Pearson

### When interested in examining how one variable changes in relation to another, which of the following descriptive statistics would you want to use?

correlation

### Correlation coefficients are used to describe

. A group

. The correlation coefficient is used to indicate the relationship of two random variables

### Which of the following illustrates the range of possible values of Pearson's product-moment correlation coefficient?

-1.0 to 1.0

### If variables change in the same direction, what type of correlation is this called?

positive correlation

### If variables change in the opposite direction, what type of correlation is this called?

negative correlation

### When data points group together in a cluster from the lower left-hand side of the xy axis to the upper right-hand side, what is this?

positive slope

### When data points group together in a cluster from the upper left-hand side of the xy axis to the lower right-hand side, what is this?

negative slope

### If the correlation between variables is .70, what percent of the variance is not shared variance?

51%

### Which of the following correlations would be interpreted as a very strong relationship?

.80

.8 to .1

### This is a situation in which the correlation between two variables begins as a direct correlation, then becomes an indirect correlation, or vice versa.

curvilinear relationship

### The coefficient of determination is equal to:

the square root of the pearson product moment correlation coefficient

. is the percentage of variance in one variable that is accounted for by the variance in the other variable.

### The amount of unexplained variance in a relationship between two variables is called:

coefficient of alienation also called coefficient of nondetermination

### A positive correlation between two variables would be represented in a scatterplot as

line sloping upwards

. all the data points are aligned along a straight line with a positive slope

### A negative correlation between two variables would be represented in a scatterplot as:

a line sloping downwards

. data points would align themselves in a straight line as well, but from the upper left hand corner of the chart to the lower right.

### If the correlation between two variables was equal to 0, the scatterplot between these two variables would be represented as:

a horizontal line

### If you wanted to compute the correlation between two interval level variables, which type of correlation should you use?

pearson

### If you wanted to compute the correlation between two nominal level variables, which type of correlation should you use?

phi

### If you wanted to compute the correlation between two ordinal level variables, which type of correlation should you use?

spearman rank

### If you wanted to compute the correlation between one nominal level variable and one interval level variable, which type of correlation should you use?

Point biserial

### If the coefficient of determination between two variables is .81, what is the Pearson correlation coefficient?

.90

### If the coefficient of determination between two variables is .81, what is the coefficient of alienation?

.19

### What is the numerical index that describes the relationships between two variables?

correlation coefficient

### The Pearson product-moment correlation examines the relationship between what type of variables?

continuous

### This measure is equal to the percentage of variance in one variable that is accounted for by the variance in a second variable.

coefficient of determination

### If X decreases in value as Y increases in value, what type of correlation exists

negative correlation

### The better your time management skills are, the more work you are able to do is an example of a ____________.

positive correlation

### The more oatmeal you eat, the lower your blood cholesterol level is an example of a ____________.

negative correlation

### You can use Pearson's correlation coefficient if one or more of your variables are ordinal or nominal. T/F

false

### When you have a direct correlation, both variables change in the same direction. T/F

True

In a direct or positive relationship, the values of both variables increase together or decrease together. That is, if one increases in value, so does the other; if one decreases in value, so does the other.

### A negative correlation indicates that variables change in opposite directions. T/F

True

In an inverse or negative relationship, the values of the variables change in opposite directions. That is, if the independent variable increases in value, the dependent variable decreases; if the independent variable decreases in value, the dependent variable increases.

### The coefficient of determination is more precise than using a correlation coefficient alone. T/F

True

page 89

### If two variables are correlated, this implies that one variable causes the other.T/F

false

correlation does not imply causation

ex on page 91

### In certain cases, Pearson's product-moment correlation coefficient can have values greater than 1.T/F

false?

page 77

### What is a correlation coefficient and what is its range?

. A correlation coefficient is a numerical index that reflects the relationship between two variables.

. Values for the correlation coefficient range between -1 and +1

### How is a direct correlation different from an indirect correlation?

A direct relationship is a relationship between two variables in which they both increase or decrease in conjunction.

A indirect relationship is in which one variable decreases as another increases.

### Is a correlation of 0.6 stronger than a correlation of -0.9? Why or why not?

no

page 79 ( the sign do not influence the strength of the correlation the absolute value is what matters)

. the absolute vale of the coefficients reflects the strength of the correlation.

### A correlation coefficient comparing exercise and body mass is -.67. What does this say about the relationship between exercise and weight?

when one variable increases, the other variable decreases

ex: as study time increases, the number of errors on an exam decreases.

### A correlation coefficient comparing study time to grades is a +.80. Can one then conclude that greater study time causes good grades?

. more of one, more of the other

. as the value of one variable increases, so does the other. For example, on average, as height in people increases, so does weight.

. positive correlation

### What is the difference between the sum of a set of values squared and the sum of the squared values?

page 82

sum of a set of values squared: taking values such as 2,3 summing them (5) and then squaring that (25)

. the sum of the squared values: taking values such as 2,3 squaring them (4,9) and then adding those together (13)