When the numbers just don't add up
Glossary
correlation. The closeness of the relationship between two variables. The correlation is positive if an increase in one variable implies an increase in the other, and negative if an increase in one implies a decrease in the other. Variables having no relationship at all are said to be uncorrelated.
model. Solving complex problems associated with real situations is often made easier by setting up a model of the situation – a mathematical description of the problem. To set up a model, a problem is simplified and only those aspects that can be represented mathematically are included.
After the problem is solved mathematically, tentative solutions are translated back to the real situation, as possible real solutions. At this stage the inadequacy of the simple model may be revealed, and some parts of the process may need to be changed. More information on models and modelling can be found at What is modelling? (Nova: Science in the news, Australian Academy of Science).
variable. Something that takes on different values that can be measured or counted. If one variable can be controlled exactly (such as the selling price of apples) then it is called an 'independent variable', while the remaining variable (in this case the number of apples bought) is called a 'dependent variable'.
Posted April 1999.