Many of the past National AP Biology lab based essay questions have asked students to “Design an experiment to…”

There are usually some common points in any question of this type. Here are some tips:

Control – use the word “control”, but also indicated several variables that are being held constant.

Ex – plants of the same species, from the same seed source, grown in the same soil and under the same conditions.

Be sure to indicate “which treatment” is serving as the control.

Hypothesis – Say the word “hypothesis” and write in the “If….then…” format.

Example – The hypothesis for this experiment is if higher light allows more photosynthesis, then the plants with the most light should have the most mass.

Tell how the experiment is manipulated (i.e. what are your treatments). Give a full range of the treatment if possible to avoid the “Three Bears Syndrome” (one too hot, one too cold, one just right)

Ex – The plants will be grown in five treatments of differing temperatures from Oo to 40o in 10 degree intervals.

Indicate to the reader what is being measured. Use quantitative measurements rather than qualitative.

Tell when then measurements will be taken. Ex – The mass of the plants will be taken in

grams at the beginning and end of the experiment.

Use a large sample size (i.e. the “rule of 10X) or show that the experiment will be repeated several times.

Ex – There will be 10 plants in each treatment and control group.

Tell the reader what you expect the results of the experiment to be and explain why.

Ex - The expected results of the experiment is that the plants with more light will have more photosynthesis, therefore, they should have more biomass.

Labs don’t have to be exactly the way they were run in AP Bio, but they should be able to work.

Be sure to give the reader sufficient background on how the method works.

Use metric units. Write clearly and with details.