AP Biology: Experimental Design and Graphing

Independent variable

variable manipulated by researcher

dependent variable

variable measured in experiment

negative control

group without experimental treatment

positive control

group with known expected result

null hypothesis

IV has no effect on DV

purpose of controls

ensure results are due to IV only

bar graph

compares categorical data

histogram

shows distribution of one variable

line graph

shows change over time

scatter plot

shows relationship between two variables

log scale graph

used for very large ranges

dual y-axis graph

compares two datasets with different units

box plot

shows median, quartiles and range