Hypothesis: A proposed explanation based on limited evidence. It is also called an intelligent guess. You use this guess as a basis to do a further investigation.
Population: The entire set of subjects or materials that you want to investigate
Sample: A part of the population that you will investigate. The sample must be a good representative of the population
Data: Pieces of factual information collected during a research
Quantitative Data: Information that can be measured and written down as numbers e.g. weight of flour, protein content in wheat grain, the density of syrup
Qualitative Data: Information that cannot be expressed as numbers e.g. color, feel, taste, aroma, appearance
Variable: A characteristic that is being observed or measured
Dependent Variable: The variable that you are measuring in an experiment. It is dependent on the value of the independent variable.
Independent Variable: The variable that you are changing in an experiment. It is independent of any other variable. A scientist changes the independent variable to see how it affects the dependent variable. For example, he may change cooking temperature (independent variable) to see how it affects the number of bacteria (dependent variable) present in a food sample after cooking.
Control: The part of the experiment that the experimenter did not change. For example, if the experimenter is changing the cooking temperature to determine its effect on the number of bacteria in the food after cooking, the control would be a sample that was not cooked. In that way, he will demonstrate that any change was attributed to the cooking.
Controlled Experiment: An experiment where all conditions remain the same except for one change.
Observational Research: A research done simply by observing and collecting data based on what is seen or heard without trying to affect the subjects being studied. For example, observing how often students select a healthy meal choice in a school canteen.
Experimental Research: A research that involves manipulating the subjects. That is, a variable is changed, and the researcher measures the effect. For example, the research may change the type of preservative in food and then measure how long it can stay on the shelf without spoiling.