What is the difference between qualitative and quantitative tests?

Qualitative tests are designed to identify the presence or absence of a substance in a sample, providing information about what is there. For instance, in laboratory analysis, a qualitative test may reveal whether a specific pathogen is present in a sample, but it will not specify how much of that pathogen is present. On the other hand, quantitative tests focus on measuring the actual amounts or concentrations of a substance, giving precise numerical data regarding how much of a particular component is in the sample. For example, a quantitative test might indicate that there are 100 colony-forming units per milliliter of a specific bacteria in a sample, allowing for a clear understanding of the extent of contamination or infection.

The other options present incorrect associations between the types of tests and their purposes. Some suggest that qualitative tests measure concentrations, which is not accurate since this is a primary function of quantitative tests. Others might confuse the nature of the tests focusing on purity or specific physical changes like color or temperature, which do not accurately reflect the fundamental differences between qualitative and quantitative analyses.