The independent variable that researchers intentionally vary is 'a) nutrient concentration of growth medium,' with units in 'b) micromolar.' The provided details explain how to identify the independent and dependent variables in an experiment, using examples of bacterial growth on gel and plant growth influenced by various factors. Option a and b are the correct options.
The variable that researchers intentionally vary in an experiment is known as the independent variable, which is manipulated to observe its effect on the dependent variable. In the context of the student's question about a scientific experiment where researchers are investigating nutrient concentration, the independent variable is 'a) nutrient concentration of growth medium,' with the units being 'b) in micromolar.' The amount of DNA per cell is typically measured in femtograms, and the time after induction would be in hours, but these are not the independent variable in this specific question.
In the example provided regarding bacteria growth on different gels, the independent variable is the type of gel used (gel A or gel B), and the dependent variable would be the amount of bacterial growth observed after 24 hours. It's crucial for variables such as water, plant food, soil, and sunlight to be controlled in plant growth experiments to prevent them from affecting the outcome and to ensure the experiment's integrity.
For Gary's experiment, factors that he did not control, which could have influenced the results, include a) individual plant variation, b) soil temperature due to different colors of containers, c) water loss due to evaporation from the soil, and d) the effect of insects. All these factors could potentially impact the growth of the plants and therefore should be considered when interpreting the results. Option a and b are the correct options.
The appropriate question is:
what variable did the researchers intentionally vary in the experiment, and what are the units for this variable? (this is the independent variable.)
a) nutrient concentration of growth medium,
b) in micromolar average amount of dna per cell,
c) in femtograms time after induction,
d) in hours