IB Biology · first assessment 2025
Paper 1B: data & experimental skills
Paper 1B contains four data-based questions linked to experimental work and the syllabus. In the current course, SL Paper 1B is 25 marks within the combined 1 h 30 min Paper 1, while HL Paper 1B is 35 marks within the combined 2 h Paper 1. A calculator is permitted.
Independent study resource. This page summarizes publicly available syllabus skills and uses original examples; it does not reproduce official examination questions.
Microscopy & scale
Calculate magnification and actual size, use scale bars correctly, estimate densities in fields of view, and reason from micrographs.
Data summaries
Calculate and interpret means, medians, ranges, standard deviation and standard error; recognize continuous versus discrete variation.
Statistical tests
Apply and interpret t-tests and chi-squared tests, including null hypotheses, degrees of freedom and statistical significance.
Graphs & relationships
Construct and interpret bar charts, histograms, scatter graphs, line/curve graphs, logarithmic graphs and box-and-whisker plots; use r and R² appropriately.
Ecological sampling
Use quadrats, capture–mark–release–recapture, the Lincoln index and Simpson reciprocal index, while evaluating sampling assumptions.
Experimental reasoning
Identify variables, controls, uncertainty, random/systematic effects, reliability, validity, outliers, limitations and targeted improvements.
High-value calculator set
Magnification & actual size
Calculate magnification, image size or actual size with automatic mm–µm–nm conversion and full working.
Open calculatorField-of-view density
Estimate cell or stomatal density from a count within a circular microscope field of view.
Open calculatorMean, median, mode & range
Summarize biological replicate data with n, mean, median, mode, minimum, maximum and range.
Open calculatorSD & standard error
Calculate sample and population standard deviation plus standard error of the mean for replicate measurements.
Open calculatorRegression, r & R²
Fit a straight line to paired biological data and calculate slope, intercept, Pearson r and R² with a graph.
Open calculatorTwo-sample t-test
Compare two biological samples with an independent Welch t-test or paired t-test and report t, df and two-tailed p.
Open calculatorChi-squared test
Calculate χ², degrees of freedom and an approximate p-value for goodness-of-fit data or a 2×2 association table.
Open calculatorLincoln index
Estimate population size from capture–mark–release–recapture data using the Lincoln index.
Open calculatorSimpson reciprocal index
Calculate the Simpson reciprocal diversity index from species abundance counts.
Open calculatorPercentage change & difference
Calculate signed percentage change or symmetric percentage difference between biological measurements.
Open calculatorRelationships worth being fluent with
| Area | Relationship | Typical use |
|---|---|---|
| Microscopy | M = image size / actual size | Magnification, actual size and scale-bar reasoning. |
| Rates | rate = Δquantity/Δtime | Growth, reaction/physiology rates and graph gradients. |
| Sampling | Lincoln: N = n₁n₂/n₃ | Capture–mark–release–recapture population estimates. |
| Diversity | D = N(N−1)/Σn(n−1) | Simpson reciprocal diversity index. |
| Genetics | p + q = 1; p² + 2pq + q² = 1 | HL Hardy–Weinberg predictions. |
| Statistics | SD, SE, t, χ², r and R² | Spread, uncertainty, significance and strength of fitted relationships. |
A reliable way to attack a Paper 1B question
- Identify what was measured, the units, sample size and any uncertainty/error bars.
- Describe the pattern before explaining it: direction, shape, maxima/minima, scatter and outliers.
- Choose a calculation or statistical test that matches the data type and experimental design.
- Separate correlation from causation and statistical significance from biological importance.
- For sampling questions, state the assumptions that connect the sample to the population.
- For evaluation, link a specific limitation to its likely effect and a targeted improvement.
Try 24 original Paper 1B tasks Experimental skills checklist