Do you change experiemnt if answer is clear?

[Marci]

We have done an experiment to see the effects of formaldehyde on plants. The experiment was an initial dose that was to be followed by a second dose a week later. It is a week later and the first dose clearly has all but killed the plant. In a few days, we'll have full death. So if the original experiment was to dose twice, is it scientifically sound not to repeat the dose since the obvious result was death? would you just report it as such in your observation/conclusion? We have started a new set of plants with half the dose to see if the result is not so severe and will report those findings as well. Finally, the dog knoked over the control plant and it broke the stems, thus giving it the illusion of drooping. Do we start with a new control and note the "dog incdient" in the report? Anyone that can help we wouuld be very appreciativie for my 5th grader!

[deleted-71827]

Hi!
I would suggest that repeating the experiment is always scientifically sound, because it is always good to repeat the experiment to make sure that the result (in this case being death) is actually what is "expected" and accurate. In terms of the control plant, I think it would be okay to start a new control plant, although of course it is always best to grow the controls and the sample plants in the same conditions (temperature, humidity, etc). It may be hard to physically compare the appearance of your sample plants with the control plant if you start a new control, and the timing will also be off as you will not have as many days of observation for the control plant as you do for the other plants. However, if time permits, I would do another control plant just to be as precise as possible. Any observations made should be in the observation section as well, because it is important information that readers will want to know so that if they ever want to repeat the experiment, they can compare their results with the ones from this experiment. Hope this helps!