Final answer:
The dependent variable in Lauren's experiment is the growth of the African violets, and the independent variables are the locations of the plants. Other growth factors like watering, plant food, soil amount, and soil type should be controlled to ensure the experiment's accuracy.
Step-by-step explanation:
In Lauren's situation with the African violets, the dependent variable is the growth or health of the plants, since it is what she is observing and measuring in response to the different conditions. The independent variables are the locations where the plants are placed (balcony, kitchen window, mantel in the living room), as these are the conditions that Lauren is changing to see how they affect the growth of the African violets.
To have a controlled experiment, Lauren should keep other factors constant that may affect plant growth, such as the amount of water (which she is already controlling), the amount of plant food, the amount of soil, and the type of soil.
If Lauren's experiment were setup like Gary's - with a focus on the amount of sunshine - she might control for things like individual plant variation, soil temperature due to different colors of containers, water loss due to evaporation from the soil, and the effect of insects which may attack one set of plants but not another.