LearnChemE

#### Correlations: Screencasts

Explains correlations.

We suggest that after watching this screencast, you list the important points as a way to increase retention.

Changes units in a correlation.

We suggest that after watching this screencast, you list the important points as a way to increase retention.

##### Important Equations:

To change a correlation from a variable with a certain set of units, $$x$$, to the same variable with a different set of units, $$x’$$, you must relate those variables and substitute that relationship back into the correlation. For example, let’s say you found a helpful correlation, but it used different units than what you would like to use. The correlation is

$y\,=\,4.6x\,+\,3$

where $$x$$ is a velocity in units of ft/min, and you would like to use $$x’$$ with units of m/s. So this is the relationship:

$x\left(\frac{ft}{min}\right)\,=\,x’\left(\frac{m}{s}\right)\left(\frac{3.785\,ft}{1\,m}\right)\left(\frac{60\,s}{1\,min}\right)$

$x\left(\frac{ft}{min}\right)\,=\,227.1\,x’\left(\frac{m}{s}\right)$

Now we can substitute that back into the equation to get this:

$y\,=\,4.6\,(227.1\,x’)\,+\,3$

$y\,=\,1044.7\,x’\,+\,3$