What does "interactive effect" mean (in science)?
I am a bit confused with this phrase, but how I interpreted it is that it involves examining the effects of two independent variables on a dependent variable. For instance, examining the effect of different percent strengths of a certain chemical on cells, as well as examining different amount of that chemical on cells .
Your interpretation is correct! In science, an "interactive effect" refers to the combined effect of two or more independent variables on a dependent variable. It involves examining how the effects of one independent variable may differ depending on the levels or values of another independent variable.
To further illustrate this, let's go back to your example of examining the effects of different concentrations and amounts of a chemical on cells. In this case, the concentration and amount of the chemical are the two independent variables, while the response of the cells (e.g., cell viability or growth) is the dependent variable.
By conducting experiments with various combinations of concentration and amount, you can determine whether there is an interactive effect between these two variables. For instance, you might observe that when the concentration of the chemical is low, increasing the amount has a minimal effect on cell response. However, when the concentration is high, increasing the amount significantly impacts the cell response. This would indicate an interactive effect, as the effect of the amount of the chemical depends on the level of concentration.
To study interactive effects, researchers often use factorial designs, where each level or value of one independent variable is combined with every level or value of the other independent variable. Analyzing the results of such experiments can provide insights into the complex relationships between variables and help understand how they interact to produce a particular outcome.