Ideas and why they were discarded

I realised I have had a number of ideas for my research project, most of which I have discarded.

1. Measuring amount of metals in soils and seeing whether this increases near roads. The independent variable would be the distance from the road, and the dependent variable would be the amount of metal. This would have been a good experiment, but it might be hard to measure the exact distance between roads, and there could be other variables such as the number of cars on the particular road, and the natural type of soil. Another practical consideration was the method of isolating metal from the soil: using magnets would only collect magnetic metals.

2. Investigating the relative success rates of various types of memorisation. The independent variable being the type of memorisation (listening, reading, looking at pictures) and the dependent variable being the number remembered correctly from the list. However, this would be difficult to find enough people, and other variables such as age and gender may be unevenly distributed among the sample groups. It might be hard to make a hypothesis, as it is difficult to find a starting point on what is likely to be the most successful method.

3. Does applying topical antiseptic/antifungal cream to a plant prevent or treat disease? The independent variable would be the type of cream used, and the dependent variable would be how long the plants survived before being overcome by the disease, or, if using baby plants, what height they grew to still having the disease.

This would be difficult to measure accurately, as the variables would be hard to control, including the initial dose of disease introduced to infect the plant (I was thinking of grinding up infected leaves from other plants and either sprinkling them in the plants or putting them in water then pouring it on the plants). Also, the plant disease may be a virus, which would not react to antiseptic or antifungal treatment.

4. How much wind can bean plants tolerate before they die? This would be quite easy to control in terms of variables, by sitting each plant in front of a fan on a particular setting for an hour a day. The independent variable would be the fan setting, and the dependent variable would be whether the plants die and the height they reach. Again, it could be difficult to control all variables, because even if the plants were put in front of the same fan, there would be a risk that other factors, such as the time of day the "wind" occured, that might affect the experiment. There is also the risk that the plant disease infecting my other plants would reach experimental plants and destroy the experiment.

5. How far from light can a bean plant grow from? According to thinkquest.com, the process of plants growing toward light is called "phototropism", and occurs as a result of a chemical called auxin (http://library.thinkquest.org/15215/Friend/plants.html). This would be interesting to investigate. The bean seed could be planted 1cm deep in all the pots, but each one would be covered with a different length of tube.

The independent variable would be the tube length, and the dependent variable would be whether the plants lives, and grows up the tube to the light, or fails to germinate or dies. However, this might present difficult-to-control variables including the fact that a plant with a shorter tube would not only be closer to light; it would get more light due to the angles of rays entering. It might also be cooler at the bottom of a long tube, or less water might be lost, creating other variables.