Behavioral Science

Biostatistics 211
What is a dependent variable?
How do I remember this?
What is the correlation coefficient (r)?
Why is it important to take the absolute
value of the r?
What is the definition of standard
deviation (σ)?
How is standard deviation used?
It is the outcome that is measured and
affected by the experiment.
The dependent variable is dependent on
the independent variable.
It expresses the strength of a relationship
between two variables. Its value must
be between −1.0 and +1.0.
Note: The minus sign (−) implies a
negative correlation and the plus sign
(+) implies a positive correlation.
The absolute value of r will determine
the strength of the correlation.
It is the root mean square deviation from
the average. The standard deviation is
defined as the square root of the variance.
It is a measure of how dispersed a data
set is around the mean. With a large σ,
data will be more spread out than with a
small one—even if the mean is the same.
0.15% 2.35% 13.5% 34.0% 34.0% 13.5% 2.35% 0.15%
−3 −2 −1 Mean +1 +2 +3
68%
95%
99.7%
Figure 27.2 Normal (Gaussian) distribution represented by a Bell-Shaped Curve. The (+) and (−)
numbers under the curve correspond to the standard deviations from the mean.