Page |1
Psych 505 Final Exam Study Guide
Questions and Correct Answers/ Latest
Update / Already Graded
Describe the difference between probability and non-probability
sampling.
Ans: PROBABILITY: KNOWN chance of being selected NON -
PROBABILITY: UNKNOWN chance of being selected
Sampling unit
Ans: -unit of analysis based on research objectives
-basic unit for sampling
-ex. schools in educational psychology
Population
Ans: entire group under study as specificied in the research
objectives
-ex. US Census population
-ex. 2022 on-campus MAPP cohort
All rights reserved © 2025/ 2026 |
, Page |2
Sample
Ans: subset of the population that should represent the entire
group --> used to estimate population values
-ex. 2022 on-campus MAPP cohort OUT OF masters students at
USC
Census
Ans: accounting of everyone in the population
**mutually exclusive from a sample
Sampling error
Ans: -any error in a survey that occurs because a samp le is used
-difference between the population value and the sample
estimate (usually unknown)
CAUSES
-method of sample selection
-sample size (the larger the sample size, the closer you get to
the population, smaller sampling error)
All rights reserved © 2025/ 2026 |
, Page |3
Sampling frame
Ans: master list of all the members of the population
Sampling frame error
Ans: over/under-representation of true population in the
sampling frame
-ex. SC Edison: particularly hot month in September, new users
--> there is an error because they came into sampling frame
after August when it was measured
Random sample
Ans: when every member (sampling unit) of the population has
an equal chance, or probability, of being selected into the
sample
Non-probability sample
Ans: when every member (sampling unit) of the population
have not been enumerated and do not have an equal chance of
being selected
Probability sampling
All rights reserved © 2025/ 2026 |
, Page |4
Ans: -random sample
-key component of study design
-all members of the population have been enumerated
-chance selection can be expressed as a probability
-probability samples are based on random sampling
-only probability samples will result in representative samples
-probability samples have high generalizability
EXAMPLE
-USC students, everyone has one email address associated with
USC
-can be selected within THIS POPULATION because there is
only 1 email
-know the probability of being accepted into sample has high
generalizability
Non-probability sample
Ans: all members (sampling unit) of the population have NOT
been enumerated and do not have an equal chance of being
selected
Non-probability sampling
All rights reserved © 2025/ 2026 |
Psych 505 Final Exam Study Guide
Questions and Correct Answers/ Latest
Update / Already Graded
Describe the difference between probability and non-probability
sampling.
Ans: PROBABILITY: KNOWN chance of being selected NON -
PROBABILITY: UNKNOWN chance of being selected
Sampling unit
Ans: -unit of analysis based on research objectives
-basic unit for sampling
-ex. schools in educational psychology
Population
Ans: entire group under study as specificied in the research
objectives
-ex. US Census population
-ex. 2022 on-campus MAPP cohort
All rights reserved © 2025/ 2026 |
, Page |2
Sample
Ans: subset of the population that should represent the entire
group --> used to estimate population values
-ex. 2022 on-campus MAPP cohort OUT OF masters students at
USC
Census
Ans: accounting of everyone in the population
**mutually exclusive from a sample
Sampling error
Ans: -any error in a survey that occurs because a samp le is used
-difference between the population value and the sample
estimate (usually unknown)
CAUSES
-method of sample selection
-sample size (the larger the sample size, the closer you get to
the population, smaller sampling error)
All rights reserved © 2025/ 2026 |
, Page |3
Sampling frame
Ans: master list of all the members of the population
Sampling frame error
Ans: over/under-representation of true population in the
sampling frame
-ex. SC Edison: particularly hot month in September, new users
--> there is an error because they came into sampling frame
after August when it was measured
Random sample
Ans: when every member (sampling unit) of the population has
an equal chance, or probability, of being selected into the
sample
Non-probability sample
Ans: when every member (sampling unit) of the population
have not been enumerated and do not have an equal chance of
being selected
Probability sampling
All rights reserved © 2025/ 2026 |
, Page |4
Ans: -random sample
-key component of study design
-all members of the population have been enumerated
-chance selection can be expressed as a probability
-probability samples are based on random sampling
-only probability samples will result in representative samples
-probability samples have high generalizability
EXAMPLE
-USC students, everyone has one email address associated with
USC
-can be selected within THIS POPULATION because there is
only 1 email
-know the probability of being accepted into sample has high
generalizability
Non-probability sample
Ans: all members (sampling unit) of the population have NOT
been enumerated and do not have an equal chance of being
selected
Non-probability sampling
All rights reserved © 2025/ 2026 |
