Psy 232 Review Psy 231: statistics. 

Include each question followed by its answer.

Name and define the four numerical scales, and note an example of each.

Write the formal definitional equation for the following [do NOT use SS]:

A sample mean

A sample standard deviation

A standard score

A linear relation, using statistical symbols

What does it mean to the researcher when she sees the standard deviation (s) of a distribution is quite large? 

What does it mean... quite small?  In practical terms, why does the size of s matter? 

Sketch a graph for each of the two distributions.

How many degrees of freedom are there in a standard deviation?  Explain why. 

How many degrees of freedom are there in a correlation?  Explain why.

Name and explain the three characteristics of a relation measured by a correlation.

Explain "standard error" in regression.  How is it related to the size of the correlation coefficient?

When we are using linear regression to predict scores (usually called Y-scores), we are interested

in the relations among the Y-mean, Y-predicted, and the actual Y-score that we are trying to predict. 

Explain why we use the Y-mean as our comparison point for deciding how accurate our prediction is.

For the variable Y, let Ym = the Y-mean, Ya = an actual Y-score, and Yp = Y-predicted.

Write an equation using the foregoing three symbols depicting how the total variability in a distribution

 is partitioned between what we can explain based on the regression solution between X and Y scores,

and what we cannot explain, and label the parts with total variability, explained variability,

and unexplained variability.

In the foregoing equation, which portion is a function of one's Independent Variable (i.e., the "X" variable)?

Sketch a graph depicting the foregoing partition, and provide the appropriate labels for all parts.