This fictional classroom experiment examined whether changing the duration of daily light exposure was associated with differences in seedling growth. Twenty-four bean seedlings were divided into two groups of twelve. One group received eight hours of light each day, while the other received twelve hours. Both groups were watered with 40 millilitres of water per pot every other day and were observed for fourteen days. The pots contained the same type of soil and were kept in the same room. The exercise was designed to practise interpreting a small dataset, rather than to establish a general rule for growing beans.

At the end of the observation period, mean height was 11.2 centimetres in the eight-hour group and 13.6 centimetres in the twelve-hour group. The difference between the means was therefore 2.4 centimetres. Two seedlings in the eight-hour group developed yellow leaves, compared with one in the twelve-hour group. No seedling died during the experiment. These observations are consistent with a possible relationship between light exposure and growth under the conditions used. They do not, by themselves, prove that longer exposure caused the difference in height.

Several limitations affect the interpretation. Seedlings were assigned to groups by their position on a tray rather than through a random allocation procedure. The initial height of each seedling was not recorded, so the groups might have differed before treatment began. Light intensity was also not measured. Although the two groups occupied the same room, their distance from the lamp was not identical. Any of these factors could contribute to a difference between the final means. The dataset does not include enough information to estimate the size of each contribution.

A follow-up experiment should record initial height, assign seedlings randomly and measure light intensity at each pot. It should also use more than one tray for each light condition. Repeating the procedure would help determine whether the observed pattern is stable. The present results support a cautious hypothesis about light exposure, but they do not identify an optimum lighting schedule. Reporting the limitations is therefore part of explaining the result, not a reason to discard the exercise.
