The sample of epidermal cells were taken from two onions instead of one onion (layer 6-10 from the first onion, layer 1-4 from the second onion) due to the time limit of experiment which may cause an inconsistency in raw data because the two onions are slightly different in preserved temperature, shape, and growing environment. When cell samples were taken from the second onion, some of the cells are frozen due to the preservation which causes a distortion of the shape of the cells and may result in errors of counts.
Because of the time limit of this experiment, there is a limitation in the size of samples. When counting the cells, there is no strict rule on regarding or disregarding part of a cell. The researcher estimated the number and may cause an error in counting. The standard deviation is much smaller than one third of each mean, and gives the data more reliability The exponential function does not fit the means well enough that for layer 9, 6, 5, 3, 2, 1, the value according to the function is not included in the range of the mean plus or minus the standard deviation.
Use consistently one onion for the experiment. Preserve the samples with restricted conditions. (Preserved time, temperature, moisture) Collect more samples.
Restrict the proportion of length that a cell has in the range of scope to be regarded in the counting.