Error free data
Suppose we have a set of data comprising
two related variables. As an example we take the cm and the
inch: 1 inch = 2.54 cm, the two variables are linearly related.
We compute the number of centimeters for 1, 2, 3 ... 10 and
put these in a graph with inches on the X-axis and centimeters
on the Y-axis. The X-axis comprises the independent variable
(inch), the Y-axis the dependent variable. We use a calculator,
and as no measurements are performed there are no measurement
errors either. Obviously the data are on a straight line which
passes through the origin. The relationship can be described
in mathematical form:
Y = a + b·X
where
Y is in cm, X in inch
a is the intercept, the value of Y when X = 0; in this case a = 0.
b is the slope, in this example 2.54.