Design an experiment: bean germination with controls
Identify 10-20 variables that may affect seed germination, select one, form a hypothesis about why it matters, determine positive and negative controls, run three bags per condition, tabulate and graph the data, write a lab report and record a one to two minute video summary.
Editorial process
Last reviewed · August 13, 2026
What the two controls have to be, given your variable
The design decision that everything else rests on is the pair of controls, and the brief is unusual in asking for both a positive and a negative one. A positive control is a condition you already know produces germination — beans on a moist paper towel at room temperature in the dark, the conditions in the procedure — and it proves your beans were viable and your technique worked. A negative control is a condition you already know prevents it, most simply beans kept completely dry. Without the positive control, a null result is uninterpretable: you cannot tell whether your variable suppressed germination or your seeds were dead. Without the negative control you have no baseline for what zero looks like. Both must differ from your test condition in only the one variable you are testing, which is what the instruction means by making it reproducible.
Choose the variable with the data collection in mind, because you have seven to ten days and thirty beans per condition. Temperature, light exposure, water quantity, soaking time, salinity and pH are all workable, and all of them can be varied while holding everything else constant using the bags and the taped placement the procedure describes. Then be careful about what you record. Germination rate as a percentage of the ten beans per bag, with three bags per condition, gives you replicates and therefore a mean and a spread — that is why the procedure specifies three. Days to first sprout is a second, different measurement and is worth collecting alongside it. Choose the graph type to match: a bar chart compares final germination percentage across conditions, while a line graph shows germination accumulating over the days. The report should state the hypothesis as a prediction with a reason, not as a guess.
Likely learning objectives
Inferred from the brief — check these against your own rubric.
- 01Identify the environmental and biological variables that affect seed germination.
- 02Form a hypothesis that predicts an effect and states a reason for it.
- 03Distinguish positive from negative controls and justify each for a given design.
- 04Use replication to produce a mean and a measure of spread.
- 05Select a graph type appropriate to the measurement being reported.
Read the full question
Review every instruction before using the planning guidance that follows.
Course-wide instructions that accompany this question
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Turn the brief into deliverables
- 01A table of 10-20 variables that may affect seed germination.
- 02One selected variable with a hypothesis explaining why it should matter.
- 03Positive and negative controls, identified and justified.
- 04A data table with title, units and three bags per condition.
- 05An appropriate graph, a completed lab report and a one to two minute video summary.
Variables, hypothesis, controls, data, report
Variables affecting germination
Ten to twenty candidates spanning water, temperature, light, gas exchange and seed condition.
The chosen variable and hypothesis
One variable selected, with a prediction and the biological reason behind it.
Positive and negative controls
A known-germinating condition and a known-failing one, each differing by one variable.
Procedure and replication
Three bags per condition, ten beans each, with placement and moisture held constant.
Data and graph
Germination percentage and days to sprout, tabulated with units and graphed appropriately.
Lab report and video
The template completed, plus a short spoken summary of the experience.
Germination requirements and experimental design
Recommended databases
- Course laboratory manual
- Plant biology textbook chapters on germination
- USDA and extension service germination resources
- Khan Academy scientific method materials
Search sequence
- 1.Read what conditions seeds require to germinate: water, oxygen, temperature and sometimes light.
- 2.Read the distinction between positive and negative controls with worked examples.
- 3.Check typical germination times for common beans so the timeline is realistic.
- 4.Read how replication supports a mean and a measure of variability.
- 5.Review which graph types suit categorical comparison and which suit change over time.
Reference shortlist
These are authoritative starting points, not a ready-made bibliography. A qualified reviewer must confirm that each source fits the assignment and supports the claim beside which it is cited.
Nothing here is cleared for citation until you have read it.
- 01
Germination | Description, Process, Diagram, Stages, Types, & Facts
Encyclopedia Britannica · 2024
The physiological requirements for germination that determine which variables are worth testing.
- 02
Scientific method | Definition, Steps, & Application
Encyclopedia Britannica · 2024
Hypothesis formation and the role of controls, which is what the design section is graded on.
- 03
Epidemiology Of Study Design
StatPearls, NCBI Bookshelf · 2024
Control conditions and replication as design requirements rather than optional extras.
- 04
Experimental Reports 2
Purdue OWL, Purdue University · 2024
How results sections present tables and figures, for the lab report write-up.
Review before submission
Common mistakes
- Treating the negative control as a second test condition rather than a known-zero baseline.
- Omitting the positive control, which makes any null result uninterpretable.
- Changing more than one thing between the test condition and the controls.
- Writing a hypothesis as a prediction with no reason attached.
- Reporting one bag per condition and losing the replication the procedure builds in.
- Choosing a graph type that does not match the variable being plotted.
Submission checklist
- Table 5 lists at least ten candidate variables.
- One variable is selected and the hypothesis gives a mechanism.
- Both a positive and a negative control are present and justified.
- Three bags were prepared for each condition.
- The data table has a title and units, and the graph type suits the data.
- The lab report is on the supplied template and the video is one to two minutes.
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Written by
Aaron Bishop
MA, Education
assignment interpretation and research-methods coaching across disciplines
Aaron leads the EssayCrackers editorial desk. He works on how assignment briefs are read — what a rubric is actually asking for, and where students most often answer a different question than the one set.
Reviewed by
Dr. Nathan Cole
PhD, Rhetoric & Composition
Argumentation and thesis development
Nathan teaches first-year composition and directs a university writing center. He reviews EssayCrackers guides for argumentative soundness and citation accuracy.