Test 2 (pg 147-170) Flashcards
As a research method, __________ allow you to describe the relationship between two measure variables.
correlational designs
A ___________ helps by assigning a numerical value to the observed relationship.
correlation coefficient (descriptive statistics)
In addition to describing a relationship, correlations allow us to ________ from one variable to another.
make predictions
Correlations vary in their _______.
magnitude
_________ is an indication of the strength of the relationship between two variables (the strength of the relationship).
Magnitude
What are the different types of correlational relationships?
positive, negative, none, or curvilinear
The magnitude or strength of a relationship is determined by the ________ describing the relationship.
correlation coefficient
A __________ is a measure of the degree of relationship between two variables.
correlation coefficient
A correlation coefficient can vary between ____ and _____.
-1.00 and +1.00
The _______ the relationship is between the variables, the closer the coefficient is to either -1.00 or +1.00.
stronger
The _______ the relationship is between the variables, the closer the coefficient is to 0.
weaker
We typically discuss correlation coefficients as assessing a ______, ______ or ______ relationship, or no relationship at all.
strong, moderate, or weak
+or - .70 - 1.00 =
a strong relationship
+ or - .30 - .69 =
a moderate relationship
+or- .00 - .29
no relationship (.00) to weak
A correlation coefficient of either -1.00 or +1.00 indicates a __________.
perfect correlation, the strongest relationship possible.
What would it mean if the correlation for height in weight in a group of 20 people was perfect (+1.00)?
This would mean that the person with the highest weight would also be the tallest person, the person with the second highest weight would be the second tallest person, and so on down the line. (and the height and weight decreased by a set amount each time.)
If there was a perfect negative correlation in the 20 person height/weight study, what would that mean?
This would mean that they person with the highest weight was the shortest, and so on, and that the height increased and the weight decreased by a set amount for each individual.
A correlation coefficient of _______ represents a perfect relationship, while a coefficient of ______ indicates no relationship.
+ or - 1.00 = perfect
0.00 = none
A ________ is a figure that graphically represents the relationship between two variables.
scaterplott
In a ______, two measurements are represented for each participant by the placement of a marker.
scatterplot
The stronger the correlation, the _______ the data points cluster around an imaginary line through their center.
more tightly
When there is a perfect correlation, where do the data points fall on a scatterplot?
the data points all fall on a straight line.
Describe what a positive relationship would look like on a scatterplot.
The majority of the data points fall along an upward angle, from lower left corner to upper right corner. The relationship is linear, and the stronger the correlation, the closer to the imaginary straight line the points will be.
Describe what a negative relationship would look like on a scatterplot.
The majority of the data points fall along an downward angle, from upper left corner to lower right corner. The relationship is linear, and the stronger the correlation, the closer to the imaginary straight line the points will be.
A negative correlation indicates that an ______ in one variable will lead to an _______ in the other variable.
increase, decrease, or decrease, increase
A positive correlation indicates that an ______ in one variable will lead to an _______ in the other variable.
increase, increase, or decrease, decrease
Describe what no relationship would look like on a scatterplot.
the data points are scattered in a random fashion. The correlation coefficient would be 0 or very close to 0 (the example in the book was -.09)
A correlation coefficient of 0 usually indicated no meaningful relationship. However it is also possible for a correlation coefficient of 0 to indicate a _________.
curvilinear relationship
A graph represents the relationship between psychological arousal (the x-axis) and performance (y-axis). The individuals perform better when they are moderately aroused than when arousal is either very low or very high. The correlation coefficient for these data is also very close to 0, being -.05. What type of relationship is this? What does the scatterplot look like?
- curvilinear relationship (so the correlation coefficient does not represent the high correlation seen in the scatterplot)
- the points are tightly clustered in an inverted U shape
correlation coefficients tell us only about _______ relationships.
linear
List the type of relationship for the following examples: smoking and cancer Intelligence and weight mountain elevation and temperature memory and age
smoking and cancer = positive
Intelligence and weight = none
mountain elevation and temperature = negative
memory and age = curvilinear
Which of the following correlation coefficients represent the weakest relationship between the two variables? -.59 \+.10 -1.00 \+.76
+.10
Explain why a correlation coefficient of 0.00 or close to 0.00 may not mean that there is no relationship between the variables.
A correlation coefficient of .00 or close to .00 may indicate no relationship or a weak relationship. However, if the relationship is curvilinear, the correlation coefficient could also be .00 or close to this. In this case, there is a relationship between the two variables, but because the relationship is curvilinear, the correlation coefficient does not truly represent the strength of the relationship.
The most common error made when interpreting correlations is assuming that the relationship observed is ______ in nature - that a change in variable A causes a change in variable B.
causal ***correlations simply identify relationships - the do not indicate causality
What is wrong with the statement “Lets stop drug use in schools by making sure they can all read.”
illiteracy does not cause drug use, Even if there is a strong positive correlation between drug use and illiteracy.
(the assumed causality and directionality)
______ is the assumption that a correlation indicates a causal relationship between the two variables.
causality
_____ is the inference made with respect to the direction of a causal relationship between two variables.
directionality