Build a falsifiable investigation and evidence portfolio

Mechanism before a label

A useful investigation begins with a mechanistic question and competing predictions. Define the independent variable, measured response, units and experimental unit before choosing a graph or test. A control is useful because it distinguishes explanations, not merely because it is called a control.

Replication must match the causal claim. Multiple measurements from one biological preparation improve measurement precision but do not necessarily replicate a treatment independently. Random assignment reduces systematic allocation bias; blinding can reduce scoring bias. Neither guarantees that every confound is removed.

Keep the first prediction, raw records, exclusions and later interpretation separately dated. Report missing data and uncertainty rather than replacing inconvenient values. A synthetic investigation can demonstrate analysis practice, but not physical laboratory participation or independently assessed practical skill.

Predict, compare and calculate

The following record is an original synthetic teaching dataset. Its assigned conditions are not a claim that an actual organism was measured. Write your prediction before revealing the changed condition.

Independent preparation responses	Value (response units)
Control preparation1	10
Control preparation2	12
Control preparation3	11
Treatment preparation1	16
Treatment preparation2	18
Treatment preparation3	17

Six independently assigned fictional preparations, three per condition.

Your prediction before comparison

This scratch prediction is not saved automatically. Copy it to the lesson notebook to retain it.

Evidence conditionReference comparisonChanged condition / follow-up

Build a falsifiable investigation and evidence portfolio

Supplied synthetic evidence: Six independently assigned fictional preparations, three per condition.

Independent preparation responses: reference condition

Quantity	Value	Unit
Control preparation1	10	response units
Control preparation2	12	response units
Control preparation3	11	response units
Treatment preparation1	16	response units
Treatment preparation2	18	response units
Treatment preparation3	17	response units

Task: Draft a one-page preregistered paper-only study with two competing mechanisms and a measurement that would separate them.

Three replicates per group provide limited precision; no causal inference beyond this stipulated assignment follows.

Compare with the conditional interpretation

Control mean11; treatment mean17; difference6 units.

The arithmetic contrast is unchanged by the design description:17−11=6. The inferential strength changes because the independent unit changes. Counting rows alone cannot establish sample size for the treatment claim.

Case index for this investigation

0. Build a falsifiable investigation and evidence portfolio
1. Connect molecular change to organism and population evidence
2. Audit mixed evidence before revealing a worked response
3. Defend conclusions, identify gaps and plan next evidence

No numerical confidence, laboratory credit or independent mastery is inferred from opening a supplied case. Save your first prediction and comparison in the notebook.

Reset this unsaved comparison

Worked reasoning

The arithmetic contrast is unchanged by the design description:17−11=6. The inferential strength changes because the independent unit changes. Counting rows alone cannot establish sample size for the treatment claim.

Control mean11; treatment mean17; difference6 units.

Apply to a new case

Draft a one-page preregistered paper-only study with two competing mechanisms and a measurement that would separate them.

Compare your reasoning with the worked response

State both predictions, assignment unit, conditions and negative/positive controls; retain raw data, units, missingness rules and a justified uncertainty method. Explain which outcome would weaken each mechanism and identify what a simulated study cannot establish.

This public response supplies feedback, not a score for independent reasoning. Record which part of your prediction changed and why.

Evidence and investigation boundary

Three replicates per group provide limited precision; no causal inference beyond this stipulated assignment follows. Technical repeats cannot isolate a treatment effect from preparation-specific differences.

For a supervised investigation, predeclare the question, biological unit of replication, treatment/comparison assignment, quantities and units, exclusion rules, graph and uncertainty method. Keep the raw records and the first prediction separate from later revisions. A simulated case does not supply laboratory hours or establish AP authorization. No physical manipulation is required by this lesson.

Source and continuation

Framework topics: Cumulative science practices. Current AP Biology framework; supporting scientific reference. Sources checked 30 October 2026; all teaching wording, questions and numbers here are original. Return to AP Biology to compare this mechanism with another scale of organization.

Retain your investigation or assessment

Use the AP Biology evidence workspace to freeze your prior plan, retain reports, record feedback exposure and request an evidence-citing human review. The workspace has twelve investigation contracts, one multistage project and six mixed written assessments; submissions do not automatically establish proficiency or laboratory participation.