Science Buddies: "Ask an Expert"

Hey everybody. We are high school students looking for some data analysis for our project. Our project is the effect of UV light intensity on the survival of duckweed plants. We used milimeters to measure the distance of the UV light from the duckweed plants. We used 5 height differences including the control. For the control we used no UV light. We started out with 100 duckweed plants at each height. Every 4 days we had the tedious job of counting how many duckweed plants lived. We did this 8 times. This meant the experimenting process lasted for 32 days. Our end results showed that the higher intensity of UV light the duckweed received the lower the survival rate of the duckweed plants were. So any advice anyone would have involving data analysis would be greatly appreciated. Thank You!

Have you considered creating a line chart that compares the number of surviving duckweed plants (Vertical axis units, 0-100 surviving plants) to the number of days (horizontal axis, 0-32 days). You can plot a different line for each UV light height and one for the control. Using a different color for each line helps to differentiate them if they cross each other. Another suggestion is to use easily distinguished shapes to mark each point you plot on the chart in case you view copies of the chart in black and white.
For example, for the points for each different height, use:
Small solid circles
Small hollow circles
Small solid triangles
Small hollow triangles
Small solid squares

If you are wondering how to interpret the results, do you have research about what might be the optimum intensity of UV light for such plants. From what your test results indicate, I wonder if the UV output of light source you used was far more intense than natural sunlight. UV light transmits a lot of energy, as you probably know if you spend long hours in the sun without sunblock. Most plant species adapt to a specific light intensity environment. Intensities that do not fall within an acceptable range are detrimental to the plant. I do not have an answer about duckweed, but perhaps some research in that light intensity area might provide an explanation.

Good luck with the analysis.

Albert Ryan