A controlled experiment is an experiment in which you change one thing (independent variable) and measure how this change affects something else (dependent variable). In a controlled experiment you design an investigation based upon background research and your hypothesis. You want to repeat this investigation at least 3 times to ensure you get the most accurate results.
During a Design Experiment you evaluate different designs by testing multiple independent variables using controlled experiments. With background information, and the data collected, you analyze your results to identify the best features of your design. You then design, and test the best solution to see if it meets your design challenge. Remember to complete each test of your investigation at least 3 times.
A field study is an investigation in which you choose to observe and measure how one thing (Independent variable) affects another (dependent variable). For this type of investigation you do not change anything in the environment yourself but rather take data on the conditions that already exist. Based on background research and your hypothesis you may choose to obtain data in different locations, at different times, etc. In an investigation with animals you will be observing and quantifying the animals’ behaviors or location (dependent variable) based upon factors you choose (independent variable).
A secondary research investigation comes from numeric data (collected by other scientists). After obtaining background information, you will create a hypothesis about how one thing (independent variable) affects another (dependent variable). By comparing data sets on these two variables, you will be able to determine whether or not your hypothesis is supported. In general you will want to use multiple datasets that have not been compared to each other before.