,PSYC 255 Quiz 4 | Introduction to Research (2026) Q&A |
Liberty University
1. Which of the following is the primary distinction between a probability and a
nonprobability sampling procedure?
A) Probability sampling involves random selection, while nonprobability sampling
does not
B) Probability sampling is only used in experiments, while nonprobability sampling is
used in surveys
C) Nonprobability sampling always produces a representative sample
D) Probability sampling is less time-consuming than nonprobability sampling
Correct Answer: Probability sampling involves random selection, while
nonprobability sampling does not
Rationale: In probability sampling, every member of the population has a known,
nonzero chance of being selected, which allows for generalizability. Nonprobability
sampling does not involve random selection, so the likelihood of any individual being
chosen is unknown, limiting the ability to generalize the findings.
2. A researcher places all potential participants' names in a hat and draws names to
determine who will be in the study. This is an example of which sampling procedure?
A) Simple random sampling
B) Stratified random sampling
C) Convenience sampling
D) Quota sampling
,Correct Answer: Simple random sampling
Rationale: Simple random sampling is a probability sampling method in which
every member of the population has an equal chance of being selected. Drawing
names from a hat is a classic illustration of this procedure, as it ensures no bias in the
selection process and gives each individual an equal probability of inclusion.
3. What is the primary purpose of random assignment in an experiment?
A) To ensure the sample is representative of the population
B) To increase external validity
C) To make the groups equivalent at the start of the experiment
D) To eliminate the need for a control group
Correct Answer: To make the groups equivalent at the start of the experiment
Rationale: Random assignment involves placing participants into groups purely by
chance, which helps ensure that the groups are equivalent on all variables at the start
of the experiment. This controls for confounding variables and strengthens the ability
to draw causal conclusions. Random assignment is different from random sampling,
which is about selecting participants from a population.
4. Which of the following is a type of nonprobability sampling procedure?
A) Simple random sampling
B) Systematic sampling
C) Snowball sampling
, D) Stratified random sampling
Correct Answer: Snowball sampling
Rationale: Snowball sampling is a nonprobability technique where existing
participants recruit future participants from their acquaintances. This method is
useful for accessing hard-to-reach populations but does not involve random
selection, so it cannot guarantee a representative sample. Simple random, systematic,
and stratified sampling are all probability methods.
5. A researcher wants to ensure that a sample reflects the ethnic diversity of the
university population. She divides the population into ethnic groups and randomly
samples from each group. Which sampling procedure is she using?
A) Simple random sampling
B) Stratified random sampling
C) Cluster sampling
D) Convenience sampling
Correct Answer: Stratified random sampling
Rationale: Stratified random sampling involves dividing the population into strata
(subgroups) based on a characteristic like ethnicity, and then randomly sampling
from each stratum. This ensures that key subgroups are represented proportionally in
the sample, which enhances the representativeness and generalizability of the
findings.
6. What does the term "effect size" refer to in research?
Liberty University
1. Which of the following is the primary distinction between a probability and a
nonprobability sampling procedure?
A) Probability sampling involves random selection, while nonprobability sampling
does not
B) Probability sampling is only used in experiments, while nonprobability sampling is
used in surveys
C) Nonprobability sampling always produces a representative sample
D) Probability sampling is less time-consuming than nonprobability sampling
Correct Answer: Probability sampling involves random selection, while
nonprobability sampling does not
Rationale: In probability sampling, every member of the population has a known,
nonzero chance of being selected, which allows for generalizability. Nonprobability
sampling does not involve random selection, so the likelihood of any individual being
chosen is unknown, limiting the ability to generalize the findings.
2. A researcher places all potential participants' names in a hat and draws names to
determine who will be in the study. This is an example of which sampling procedure?
A) Simple random sampling
B) Stratified random sampling
C) Convenience sampling
D) Quota sampling
,Correct Answer: Simple random sampling
Rationale: Simple random sampling is a probability sampling method in which
every member of the population has an equal chance of being selected. Drawing
names from a hat is a classic illustration of this procedure, as it ensures no bias in the
selection process and gives each individual an equal probability of inclusion.
3. What is the primary purpose of random assignment in an experiment?
A) To ensure the sample is representative of the population
B) To increase external validity
C) To make the groups equivalent at the start of the experiment
D) To eliminate the need for a control group
Correct Answer: To make the groups equivalent at the start of the experiment
Rationale: Random assignment involves placing participants into groups purely by
chance, which helps ensure that the groups are equivalent on all variables at the start
of the experiment. This controls for confounding variables and strengthens the ability
to draw causal conclusions. Random assignment is different from random sampling,
which is about selecting participants from a population.
4. Which of the following is a type of nonprobability sampling procedure?
A) Simple random sampling
B) Systematic sampling
C) Snowball sampling
, D) Stratified random sampling
Correct Answer: Snowball sampling
Rationale: Snowball sampling is a nonprobability technique where existing
participants recruit future participants from their acquaintances. This method is
useful for accessing hard-to-reach populations but does not involve random
selection, so it cannot guarantee a representative sample. Simple random, systematic,
and stratified sampling are all probability methods.
5. A researcher wants to ensure that a sample reflects the ethnic diversity of the
university population. She divides the population into ethnic groups and randomly
samples from each group. Which sampling procedure is she using?
A) Simple random sampling
B) Stratified random sampling
C) Cluster sampling
D) Convenience sampling
Correct Answer: Stratified random sampling
Rationale: Stratified random sampling involves dividing the population into strata
(subgroups) based on a characteristic like ethnicity, and then randomly sampling
from each stratum. This ensures that key subgroups are represented proportionally in
the sample, which enhances the representativeness and generalizability of the
findings.
6. What does the term "effect size" refer to in research?
