Scientific experiments will normally have three types of variables; controlled, independent and dependent. Variables are a condition or factor that is used in testing a hypothesis and generating a conclusion. These three types of variables can also be quantitative or qualitative in nature.
By definition something that is qualitative concerns or describes a quality. A qualitative variable is a descriptive. Qualitative variable are sometimes referred to as categorical. The variable may be colors in the light spectrum or a comparison between red and green grapes. Qualitative variables can influence the outcome of an experiment or research because they can influence other factors or parameters. Qualitative variables are frequently used in social research. Qualitative research is considered to be inductive.
By definition something that is quantitative can be expressed as a quantity or number. Quantitative variables are something that can be measured. Quantitative variables are numerical. A quantitative variable can be a percentage of something, a number of units or any other measurement.
Temperature is a quantitative value or variable by the number of degrees. Speed, area population, voltage and time are all examples of quantitative variables that can be measured. Quantitative variables are most often considered to be deductive in nature.
Deduction and induction in experimentation and research:
Deduction works from a general idea to a specific idea. Deductive research starts with a theory, forms a hypothesis, gathers observations and then confirms or disproves the original thought.
Induction works in the reverse. Inductive experimentation will start with an observation and then look for patterns in the observation. Once patterns form a hypothesis is developed. The hypothesis is then tested for a resulting theory.
The best results in experimentation come from having only one independent variable. The controlled variable is something that does not change and must remain constant. The independent variable is the variable that is changed by the researcher. The dependent value is the variable that changes due to the independent variable.
An example of quantitative variables in an experiment would be testing the change in speed on a turntable as additional weight is applied. The turntable itself is the controlled variable. The experimenter will only use one. The independent quantitative variable is the amount of weight applied for each measurement. The dependent quantitative variable is the resulting speed that is measured.
An example of a qualitative variable in testing would be the drying time require for red and green grapes at a constant temperature. The outcome, or dependent
variable, of time is measured and therefore quantitative. The controlled variable being used is temperature, also quantitative. The independent variable is qualitative, the difference between red and green grapes. In this particular example the weight of each grape, a quantitative variable would also need to be consistent or controlled.