Interpret seed-establishment percentages and evidence limits
Calculate outcomes without claiming genotype or final yield.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall DNA, inherited characteristics, nuclei and the distinction between growth and reproduction.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the difference between seventy and sixty percent?
What you will learn
- Use matching starting totals and observation times
- Distinguish establishment from other outcomes
Interpret seed-establishment percentages and evidence limits
Invented establishment A 35/50 = 70%, B 30/50 = 60%. Difference 10 percentage points; relative increase about 16.7%. Not yet established is not necessarily dead. Original teaching model.
| Seed group | Starting seeds | Established | Not yet established |
|---|---|---|---|
| Seed group A | 50 | 35 | 15 |
| Seed group B | 50 | 30 | 20 |
| Feature | Meaning |
|---|---|
| Group A | 35 established; 15 not yet established |
| Group B | 30 established; 20 not yet established |
| Comparison | 10 percentage points; about 16.7% relative increase |
| Limit | Establishment does not establish genotype or adult yield |
Use matching starting totals and observation times
The invented nursery record starts with fifty seeds in group A and fifty in group B, each from a stated fertilised-seed history. At the same observation time, thirty-five and thirty seedlings meet the supplied establishment criterion. The criterion requires a root system and a new shoot under the specified conditions. The groups measure one nursery outcome, not every possible benefit of their reproductive route.
Establishment is 35/50 × 100 = 70 percent in A and 30/50 × 100 = 60 percent in B. The difference is ten percentage points. Relative to B’s sixty percent, the increase is 10/60 × 100 = 16.666… percent, approximately 16.7 percent to one decimal place. Identify the baseline and whether points or relative percent are requested.
Distinguish establishment from other outcomes
Fifteen seeds in A and twenty in B have not met the establishment criterion at that observation time. This does not automatically mean they are dead. The counts do not directly test genotype, disease freedom, adult crop yield or whether every offspring retained a desired trait combination. The supplied fertilisation history establishes origin; the establishment fractions do not independently prove it.
To compare wider performance, consider repeated groups, seed viability, age, stock origin, medium, water, temperature and observation period. Changing several factors can confound the comparison. A single invented outcome cannot rank sexual reproduction against all vegetative routes. The written interpretation also does not establish that a learner can perform a supervised investigation safely and competently.
Pause and explain
What does the nursery count directly establish?
Worked example
Thirty-two of forty seeds meet a supplied establishment criterion. Calculate the percentage.
Show the worked solution
- Use forty as the starting denominator.
- 32/40 × 100 = 80.
Answer Eighty percent established by the observation time.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Calculate establishment percentages and their percentage-point difference for groups A and B.
Give me a hint
Use the original groups of fifty.
Compare my reasoning
- 35/50 = 70%; 30/50 = 60%.
- 70 − 60 = 10 percentage points.
A 70%; B 60%; difference 10 percentage points.
Look for these in your work
- Use original denominators
- State percentage points
Find the relative increase from B’s fraction and the numbers not yet established.
Give me a hint
Use 60% as baseline and subtract from fifty.
Compare my reasoning
- 10/60×100 = 16.666…%.
- 50−35 = 15; 50−30 = 20.
Relative increase about 16.7% to one decimal place; not yet established A 15 and B 20, without establishing that they are dead.
Look for these in your work
- Use the relative baseline
- Retain the observation-time limit
Does group A’s higher fraction prove identical desired genotypes, disease-free adult yield or universal sexual superiority?
Give me a hint
Match each claim to what was actually counted.
Compare my reasoning
- Only establishment was counted.
- Genotype, adult yield and other routes are not directly compared.
No. The record measures establishment only; it does not prove desired-genotype identity, disease-free adult yield or universal superiority over other reproductive routes.
Look for these in your work
- Limit the outcome claim
- Identify missing comparisons
Common mistakes
- Calling ten percentage points a ten-percent relative increase.
- Calling every non-established seed dead.
What can you explain now?
What does the nursery count directly establish?
Compare with the explanation
Establishment by a defined observation time
It does not measure adult yield or genotype.
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Make it stick
Calculate both percentage comparisons and state the measured outcome’s limits.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.