Who is responsible for the invention of the Pearson product-moment correlation coefficient?
When interested in examining how one variable changes in relation to another, which of the following descriptive statistics would you want to use?
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?
If variables change in the opposite direction, what type of correlation is this called?
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?
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?
If the correlation between variables is .70, what percent of the variance is not shared variance?
Which of the following correlations would be interpreted as a very strong relationship?
.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.
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?
If you wanted to compute the correlation between two nominal level variables, which type of correlation should you use?
If you wanted to compute the correlation between two ordinal level variables, which type of correlation should you use?
If you wanted to compute the correlation between one nominal level variable and one interval level variable, which type of correlation should you use?
If the coefficient of determination between two variables is .81, what is the Pearson correlation coefficient?
If the coefficient of determination between two variables is .81, what is the coefficient of alienation?
What is the numerical index that describes the relationships between two variables?
The Pearson product-moment correlation examines the relationship between what type of variables?
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
The better your time management skills are, the more work you are able to do is an example of a ____________.
The more oatmeal you eat, the lower your blood cholesterol level is an example of a ____________.
You can use Pearson's correlation coefficient if one or more of your variables are ordinal or nominal. T/F
When you have a direct correlation, both variables change in the same direction. T/F
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
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
If two variables are correlated, this implies that one variable causes the other.T/F
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
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?
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?
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)