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You are here: Experts > Science > Science/Nature for Kids > Science for Kids > Forensics keywords
Expert: Ralph Salier-Hellendag - 11/4/2009
Question
What do these keywords mean? Please could you also give an example of each of them (if that makes sense!).
Variable
Independant variable
Dependant variable
Control variable
Reliable
Evidence
Accurate
Evaluate
Answer
Hi Rosie,
here in the states we have science fair competitions and these are key words used in these science fairs. So I will set up an experiment as an illustration for these words:
I want to compare the growth of bean plants based on the amount of water each one gets. So to do this experiment I will set up a grid and in this grid I will have pots of the same size and the same amount of soil (all of the potting soil is from the same bag) and the grid is five deep and five wide thus a total of 25 pots. Into each pot I plant one bean seed and following packaging directions water the seed into the pot. The entire arrangement is placed in a sunny protected area (it can not get rained on) and each row or column is designated to get a specific amount of water every day (Or if you choose every other day or every third day). Careful records are kept indicating seed germination time, growth etc...
My hypothesis is that plants that get more water will germinate and grow faster then those that get less water. (This is the question that this experiment will help answer at the conclusion of the experiment)
The variables are: the potting soil, the water, the pots, the amount of sun, the timing of watering, ambient sound/noise.
In this experimental setup, all of these have been made neutral except the amount of water. This makes the water the independent variable.
The dependent variable is the growth rate of the plants.
The control variable is that row or column of pots that, unlike the others are treated either with no water at all, or is watered normally, thus making it different from the others in the experimental groups.
I used beans in this example because they will reliably germinate so I should have all 25 pots growing plants. Thus reliability is important in any experiment to ensure that it will always work even under unusual circumstances.
Evidence is obtained from observation. The germination time frame, the speed of growth, the length of time to first flowers etc... these are all experimental evidences used in the development of the evaluation of the experiment. In the US, this evidence is called Observational data or material.
Accurate is how carefully these observations are made. If you only look at the grid once a day, you will be making daily observations and you will find that all of the seeds germinated at the "same time or same day". However, if you look at the grid 3 times a day, you may find that some germinated in the morning while others didn't do so until late in the afternoon. This may be more accurate but then your observations must be the same on a daily basis. You may measure the height of growth using metric or inches, where metric would be more accurate and well defined. Do you do your measurement 3 times daily or only once per day. Again, the higher the numbers of regularly scheduled measurements provides more accurate long term data.
How now to evaluate these observations and data? This is done in the evaluation stage which results in a series of conclusions and the verification of the hypothesis ( dis-proof of the hypothesis).
To help look at the data, I can make a growth chart and how quickly the plants grew etc... Then I can do some statistics showing that those plants that got x amount of water grew the fastest. This can be shown in a ratio of x amount of water per inch of plant growth.
So going back to the hypothesis that those that get more water grow the fastest can be shown to be proven or dis-proven.
I hope that this makes sense to you.
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