Components of Experiments

a. Variables (i) Independent/Manipulated Variable – changed by the investigator (ii) Dependant/Responding Variable – variable that is measured, counted or recorded by investigator

If I do ____________________ then _____________ will result. the effect with be ____________.

Dependent variable (y-axis) Independent variable (x-axis) Dependent variable (y-axis) Dependent variable (y-axis) Independent variable (x-axis) Independent variable (x-axis)

a. Variables (continued) (iii) Standardized Variables – variables that are kept equal in all treatments so that any changes in the dependent variable can be attributed to the independent variable

b. Treatment – the one where the independent variable is manipulated c. Control – that which does not receive treatment in the experiment.

d. Randomization – choose samples randomly to avoid bias. e. Sample Size – The number of organisms that are experimented on. f. Replication – The number of times you do the experiment over time; the more samples you have the better the results.

g. Size of Scope of Study (i) Lab (ii) Small-scale field (iii) Large-scale field

h. Accuracy – how close a measurement value is to the true value. i. Precision – how close the measured values are to each other.

Good accuracy and good precision Poor accuracy and poor precision Poor accuracy and good precision