Does the plotted data resemble a straight line?
•
The slope may be either positive or negative.
• Linear associations are the
most popular because they are easy to read and interpret.

Does the plotted data ascend rapidly at the left but level
off toward the right?
Remember the shape of the natural logarithmic function
crossing the xaxis at one and domain x > 0. 
Does the plotted data appear to grow (or decline) by
percentage increases (decreases)?
• Often deals with growth of populations, bacteria,
radioactive decay, etc.
Remember the shape of the exponential function, crossing
the yaxis at one and range y > 0 
Does the plotted data possess characteristics not seen in
the first three models? Not a straight line, but a
more gradual change than exponential?• Power functions
are of the form y = ax^{b}. Remember
the nature of such graphs when the exponent is odd and even.
First quadrant:
Outside first quadrant:
