Unit 3: Collecting Data Flashcards
census
when you collect data on every (ALL) individual in the population.
population
all individuals/items from which you draw for a study
sample
a subset of individuals/items from a population
bias
a study flaw that leads to unrepresentative and/or inaccurate estimates
undercoverage
When part of the population has a reduced chance of being included in a sample
nonresponse
When individuals chosen for a sample don’t respond. Leads to bias if these individuals differ from respondents
When writing about sampling bias….
- Identify the population and the sample
- Explain how the sampled individuals might differ from the general population
- Explain how this leads to an over or underestimate
voluntary response bias
Occurs when a sample is composed of volunteers, who may differ from individuals who don’t choose to volunteer.
question wording bias
When survey questions are confusing or leading
self-reporting response bias
When individuals inaccurately report their own traits
simple random sample (SRS)
a sampling method in which every possible group of individuals in the population has an equal chance of being selected
When describing how to preform a SRS…
- Assign each individual in the population a number 1 – N (population size).
- Use a random number generator to obtain n (sample size) numbers, skipping repeats.
- Sample the individuals whose numbers were generated
Control group is…
used to provide baseline data for comparison
Double blind experiment
when the subjects and experimenter are unaware of what treatment is given
Single blind experiment
when just the subjects are unaware of what treatment is given
placebo is
a fake treatment that looks just like the treatment with the “active” ingredient
placebo effect
when a fake treatment works
Steps to conduct a random assignment
1.) Label experimental units from 1-n
2.) Use a random number generator to generate the unique numbers that you place in groups (Remember your number of groups should equal the number of treatments)
3.) Assign groups to the treatments
Key Principles of Experiments
1.) Comparison (2 or more treatments)
2.) Random assignment
3.) Control group
4.) Replication (using enough experimental units to see a difference)
a block
group of experimental units that are similar
Like same grade level
Randomized Block Design
separate subjects into blocks and then randomly assign treatments within each block
choose the variable with the most affect on response
Match Pairs Design
- subjects are paired (block of size 2) and then randomly assigned to a treatment
- each subject receives two treatments, then order of treatments must be randomized
These are the two different ways to do a match pair design
