Chapter 13: Correlation and Regression Basic Stats

A correlation coefficient is used to

determine if, and how, two variables might be related to each other.

A negative correlation coefficient means that

if someone has a high score on one variable the tend to have a low score on the second variable.

If two variables have a weak relationship, the absolute value of the correlation coefficient will be close to

0

Positive z scores represent values that are

above average

The _______ of a z score indicates how much better or worse a given score is than the mean score.

absolute value

Which of the following are correlations designed to accomplish? Choose 2.

Determine if two variables are associated. Quantify the degree or strength of the association between two variables.

When, on average, both paired z scores tend to be positive or both paired z scores tend to be negative the resulting r value is

positive.

When, on average, paired z scores tend to have opposite signs the resulting r value is

negative

A negative correlation between two variables indicates that high scores on one variable are associated with ______ scores on the second variable.

low

When computing statistics by hand researchers most often use _________ formulas. When trying to understand how a statistic works students will find it easier to work with _________ formulas. However, both formulas will always produce the ________ value(s).

computational; definitional; same

If both variables being analysed are measured on an interval or ratio scale a _______ correlation should be used.

Pearson's

If the trend revealed by a scatterplot is not linear but it is monotonic what correlation should be used

Spearman's

If one of the variables is measured on an ordinal scale and the other variable is measured on an ordinal, interval or ratio scale a __________ correlation should be used.

Spearman's

A correlation can only be used if the scores on each variable

were paired or linked to each other in some way.

Which of the following statements is true about statistics and causation

No statistics are sufficient evidence for inferring causality.

If the null hypothesis is true and two variables are not associated with each other the r value should be close to

0

If an obtained r value is further from zero than the critical value you should

reject the null hypothesis.

A two-tailed critical value should be used when the research hypothesis

does not predict a specific direction for the relationship between the two variables.

In a scatterplot each dot represents

a set of paired of X and Y scores.

The research hypothesis for a two-tailed Pearson's correlation predicts that the test statistic r will be far from

0.

A two-tailed correlation has ______ critical region(s)

two

If an r2 equals .36 it means that 36% of the variability in one variable is

predicted by the variability in the other variable.

In an APA style reporting statement, the number in parentheses after r is

the df.

If you need to do a Spearman's correlation because the data are monotonic but not linear you need to convert the raw scores to _____ and then use the same steps/formulas that you would use to perform a Pearson's correlation.

ranked scores

When entering data for a correlation analysis in SPSS

each variable is in its own column.