AP Bio Unit 1

Variable

any condition that may cause a change in the system eing studied

Quantitative

measured by the quantity — numbers

Qualitative

measured by the quality

Controlled Experiment

only one variable is changed to ensure that the effect of only that one variable can be measured

Independent Variable

manipulated variable, changed by the experimenter in the design of the experiment

Dependent Variable

responding variable, what changes as a result of the change in the independent variable

Controlled Variables

variables that may change the outcome of the experiment, but since they aren’t being studied, they need to be kept constant each trial

Research Question

states the independent & dependent variable in the experiment

Research Question Example

How does the percentage of light from a lamp affect the rate of oxygen gas production from an aquatic plant?

Hypothesis

a possible answer to the research question

Control Group

a set of organisms/samples that do not receive the treatment (the independent variable) that is being studied

Alternative Hypothesis (H subscript A or H subscript 1)

a simple statement used in statistics that claims the experimental group will be statistically different from the control group

Alternative Hypothesis Example

H subscript 1: compost has an effect on tomato plant rate of growth

Null Hypothesis (H subscript 0)

a simple statement used in statistics that claims there is no statistical difference between experimental group and the control group

Null Hypothesis Example

H subscript 0: the compost will have no effect on the rate of growth of tomato plants

Experimental Hypothesis

This is a statement that specifically describes, with reasoning, how the independent variable affects the dependent variable

Experimental Hypothesis Example

IF the tomato is grown in a compost pile, THEN the rate of growth will be greater than a tomato grown in regular soil, BECAUSE there are greater amounts of nutrients available in the compost.

Negative Control

a control group in an experiment that uses a treatment that isn’t exposed to produce results

Negative Control Example

water + benedicts = no reaction

water + iodine = no reaction

Positive Control

a control group in an experiment that uses a treatment that is known to produce a positive result

Positive Control Example

glucose solution + benedicts = reaction

starch + iodine = reaction