3.2b(i) Experimental design

Question 1

Independent Variable

Answer 1

The independent variable is the variable that is changed in a scientific experiment. Can be continuous or discrete.

Question 2

Dependent Variable

Answer 2

Dependent variable is the variable being measured in a experiment. Can be continuous or discrete.

Question 3

Continuous

Answer 3

Can take on an infinitely many, uncountable values. For ex, length, concentration, wavelength.

Question 4

Discrete

Answer 4

Can have a finite range of values. For ex, colour, presence/absence, shoe size.

Question 5

Experiments

Answer 5

Experiments involve the manipulation of the independent variable by the investigator.
The experimental treatment group is compared to a control group.
The use and limitations of simple (one independent) variable and multifactorial (more than one independent variable) experimental designs.

Investigators may use groups that already exist, so there is no truly independent variable.

Question 6

Simple experiments

Answer 6

The control of lab conditions allows simple experiments to be conducted more easily than in the field. However a draw back is that it is findings may not be applicable to a wider setting.

Question 7

Multifactorial experiment

Answer 7

Involves a combination of more than one independent variable or combination of treatments.

Question 8

Observational studies

Answer 8

In these studies the independent variable is not directly controlled by the investigator, for ethical or logistical reasons. They are good sat detecting correlation, but since they do not directly test a hypothesis, they are less useful for determining causation.