Students set up an experiment to investigate the effect of changing the amount of time seedlings were exposed to light each day on their growth. They had twenty-four bean seedlings which they put into two groups of twelve. One group had eight hours of light each day and the other group had twelve hours of light each day. Both groups of seedlings were watered with 40 ml of water every other day for fourteen days and were in the same pots containing the same type of soil in the same room. The aim of the experiment was to gain experience of handling and interpreting a very small data set and not to investigate how to grow beans.

For both groups, the mean height of the seedlings at the end of the experiment was: 8 hours light – 11.2 cm; 12 hours light – 13.6 cm. A difference of 2.4 cm between the two means was found. It was also noted that two of the seedlings in the 8 hours light group developed yellow leaves while one of the 12 hours light group seedlings did the same. None of the seedlings died during the experiment. It will be noted that these results are consistent with the possibility that seedlings given longer periods of light exposure could grow greater.

There are several limitations to the data. The seedlings were assigned to the two groups of pots on the tray that they were on. The initial height of the seedlings was not recorded and so there could have been a difference in the height of the two groups of plants before they were treated. The amount of light that the two groups of plants received was not measured. The two groups of plants were in the same room and so were at the same distance from the lamp. However, the distance from the lamp for each pot in the two groups was not identical.

All of these points should be addressed in a follow-up experiment to test for the influence of light exposure on the growth of seedlings of the bean plant. In the experiment a number of tray positions would be set up for each of the light exposures, and a large number of seeds sown on each tray. The seedlings of corresponding positions on the trays would be of similar initial height. The light intensity at each pot would be measured. The results of this experiment would assist in establishing a cautious hypothesis for the influence of light exposure and would also attempt to establish an optimum lighting schedule for the seedlings.