Most biology and pharmacology theses compare a control group with one or more treatment groups — for example SOD, CAT or MDA levels in different treatment groups. A good figure makes the comparison obvious at a glance.
Choose the right chart
- Bar chart with error bars — groups on the x-axis, mean value on the y-axis. Most common.
- Dot plot / bar with individual points — shows every replicate; increasingly preferred by journals.
- Line graph — for time courses or dose–response.
SD or SEM?
| SD (standard deviation) | SEM (standard error of the mean) | |
|---|---|---|
| Shows | Spread of the individual values | Precision of the mean estimate |
| Size | Larger | Smaller (SEM = SD / √n) |
| Use when | Describing variability of the data | Comparing means (state n clearly) |
Both are accepted — the important rule is to state which one you used and the n in the figure legend: “Data are mean ± SD (n = 6).”
Showing significance
- Run the correct test first: one-way ANOVA with Dunnett (vs control) or Tukey (all pairs); t-test for two groups.
- Use stars: * p < .05, ** p < .01, *** p < .001, and explain them in the legend.
- Alternatively use letters (a, b, c): groups sharing a letter are not significantly different.
Figure checklist
- ☐ Axis titles with units (e.g. “SOD activity (U/mg protein)”).
- ☐ Control group first, then treatments in logical order.
- ☐ Same colours for the same groups across all figures.
- ☐ High resolution (at least 300 dpi) for print.
- ☐ Legend states test, n, error bar type and star meanings.
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