AP Stats Chapter 4
voluntary response bias
bias introduced to a sample when individuals can choose on their own whether to participate in the sample
nonresponse bias
bias introduced when a large fraction of those sampled fails to respond
The principle reason for the use of random assignment in designing experiments is that it
creates approximately equal groups for comparison.
The principle reason for the use of controls in designing experiments is that it
distinguishes a treatment effect from the effects of confounding variables.
response bias
leading questions, social desirability
undercoverage
occurs when some groups in the population are left out of the process of choosing the sample
Three factors of good experimental design
randomness, comparison, replication
The reason that blocking (as in a randomized block design) is sometimes used in experimentation is to
reduce variability arising from random assignment.
The principle reason for replication in designing experiments is that it
reduces sampling variability.
random allocation
to eliminate bias in the sampling process
comparison
to reduce the effect of lurking variables
blocking
to reduce variability between subjects in an experimental design
stratified random sampling does for the sampling process what
blocking does for the experimental design