IDS 270 – Final Exam Study Guide with
Definitions and Examples – DePaul
University – Comprehensive Concept
Summary
How do you calculate the average? add all values up, divide by total number of values
Average is the same thing as... Mean
Observational study We observed the behavior or ask people questions as they're going
about their day-to-day lives. Ex: call people and ask them how often they eat out.
Experiment We impose some treatment on people and then observe their behavior or ask
questions. Ex: give people a drug and then do chemical analysis of their blood.
Confounded variables Two variables where the effect of one on the dependent variable
cannot be separated from the effect of the other. Ex: if you take drugs and drink alcohol, and then
have a car accident, the effect of the drug versus the alcohol cannot be separated from each other
as the cause of the accident
Population The set of everything. Ex: all the people in America
Sample A small group pulled from the population. Ex: sample 40 voters from the
population of America
, Sample distribution The set of number within one sample
Voluntary response sampling People volunteer to give data for a study. Ex: people text a
phone number if they agree with a statement and text a different one if they disagree
Convenience sampling People are selected to be in a sample because of convenience or
low expense. Ex: mall intercepts, or asking the people on the floor of your dorm to fill out a
survey
Bias Systematically favoring a certain outcome from research
Simple random sampling Label all the people in the population with a number. Have a
computer select a set of random numbers in that range. People labeled with the number are
selected for the sample. Therefore, every person or sub-group of people has an equal chance of
being in the sample.
Stratified sampling First breaking the population into natural segments (called strata) and
then using random sampling within the strata. Ex: radio stations or types of colleges (community
colleges, public universities, private universities, standalone liberal art colleges).
Multi-stage sampling Basically practicing stratified sampling repeatedly to get a final
sample
Definitions and Examples – DePaul
University – Comprehensive Concept
Summary
How do you calculate the average? add all values up, divide by total number of values
Average is the same thing as... Mean
Observational study We observed the behavior or ask people questions as they're going
about their day-to-day lives. Ex: call people and ask them how often they eat out.
Experiment We impose some treatment on people and then observe their behavior or ask
questions. Ex: give people a drug and then do chemical analysis of their blood.
Confounded variables Two variables where the effect of one on the dependent variable
cannot be separated from the effect of the other. Ex: if you take drugs and drink alcohol, and then
have a car accident, the effect of the drug versus the alcohol cannot be separated from each other
as the cause of the accident
Population The set of everything. Ex: all the people in America
Sample A small group pulled from the population. Ex: sample 40 voters from the
population of America
, Sample distribution The set of number within one sample
Voluntary response sampling People volunteer to give data for a study. Ex: people text a
phone number if they agree with a statement and text a different one if they disagree
Convenience sampling People are selected to be in a sample because of convenience or
low expense. Ex: mall intercepts, or asking the people on the floor of your dorm to fill out a
survey
Bias Systematically favoring a certain outcome from research
Simple random sampling Label all the people in the population with a number. Have a
computer select a set of random numbers in that range. People labeled with the number are
selected for the sample. Therefore, every person or sub-group of people has an equal chance of
being in the sample.
Stratified sampling First breaking the population into natural segments (called strata) and
then using random sampling within the strata. Ex: radio stations or types of colleges (community
colleges, public universities, private universities, standalone liberal art colleges).
Multi-stage sampling Basically practicing stratified sampling repeatedly to get a final
sample
