Midterm 2 Flashcards
What is a representative sample?
A sample that accurately represents the population that you are studying.
What is a biased sample?
A sample that does not represent the targeted population, contains different characteristics and the procedure favors the selection of certain individuals in comparison to others. Can occur by chance or by selection bias.
Example of biased samples?
Researcher going door to door
Financial compensation
Survey return rate
What do we use to calculate sample size?
Power analysis
What are the major factors that influence sample size? (4)
1) Size of the difference you need to detect
2) Variability in the factor of interest
3) P value you plan to use as a criterion for statistical significance
4) How confident do you want to be that you will detect statistical significance, assuming a difference exists
Effect size (power analysis)
The difference between mean (quantitative) or proportions
(qualitative) of two groups.
What is Standard deviation?
The variability within a sample.
What is a Type 1 error?
P level, usually 0.05 (5%).
What is power (power analysis)?
The probability of finding an effect (“how confident do you
want to be of your effect”), usually 80%.
What is the Direction of effect?
It can it go up only (one-tail); up and down (two-tail)
What are the types of Statistical tests? (3)
The chi-square, t-test, etc.
What is Attrition?
An adjustment in sample size (eg. death of animals, dropout)
What is the Resource equation?
E = (Total number of animals) − (Total number of groups)
What is the E variable? (resource equation)
The degree of freedom of analysis of variance (ANOVA)
When do you use the resource equation? (4)
When you cannot predict:
1) Effect size (ie. mean).
2) Standard deviation (ie. no previous findings available).
3) Multiple endpoints measured.
4) Complex statistical procedure used.
What are the two types of non-probability sampling?
1) Convenience sampling
2) Quota sampling
What is convenience sampling?
A sampling method where participants are easy/convenient to access/reach and are available to participate.
What is quota sampling?
Identify a subgroup, then choose from each subgroup to get a quota.
What is simple quota sampling?
Sampling method where little is known about the characteristics of a target population and equal number of participants selected for.
What is proportionate quota sampling?
Sampling method where demographics are known and proportionately represented in sample.
What is animal research quota sampling? And it’s pro?
Sampling method where buying animals from single supplier and thus animals obtained have same proportion on many characteristics.
Provides a sample that is representative of target population.
What are the four probability sampling methods?
1) Simple random
2) Systematic
3) Strata
4) Cluster
What is simple random sampling?
Sampling method where all individuals have an equal chance of being selected and each selection is independent of others.
Example: Choose 10 students from this class, give all students a number, then pick 10 numbers.
What is simple random sampling with replacement?
After each selection, he/she is added back into the pool and an individual can be chosen more than once.
What is simple random sampling without replacement?
After selection, the individual is removed from the pool and the probability changes with each selection. It does not produce independent selections and guarantees that no individual is chosen more than once.
What is the warning for simple random sampling?
When participant selection is left completely up to chance, can lead to a sample that is not representative of the population.
What is systematic sampling?
Sampling method where you choose every # participant on a list. Combination of simple random sampling + systematic process.
What is stratified sampling?
Sampling method where the population is divided into strata (subgroups), then participants selected from each strata.
What is simple stratified sampling?
Obtain equal numbers from each strata
* Equal representation
* Does not represent proportions in the population
What is proportional stratified sampling?
Select a different proportion (%) from each strata.
* Proportion depends on what representation in the actual population
* Difficult to compare between strata if some strata makes up a small percent of population.
Quota vs Simple stratified sampling? (similarities and differences)
-Similarity: Subgroups are grouped together
The difference is in random selection
-Quota sampling – not randomly selecting individuals from
population. Researcher chooses who gets sampled (individuals are pre-selected out of convenience)
-Stratified sampling – randomization first then selection
What is cluster sampling?
Sampling method where the population can be identified into clusters; then choose from a proportion of the clusters.
Advantage of cluster sampling? (2)
1) Quick and easy to get a large sample
2) Can measure all individuals in groups
The disadvantage of cluster sampling?
Some clusters are completely omitted, what if something is unique about certain clusters?
What research strategy do you use when examining individual variables?
Descriptive research strategy.
What is the descriptive research strategy?
Describes the current state of a variable(s) and does not examine the relationship between variables. (Not comparing between groups)
What research strategy do you use when examining the relationship of two variables?
Correlational research strategy.
What is the correlational research strategy?
Measure two (or more) variables for every individual/subject in the group and identify correlations between variables. Measures relationship between variables - As one variable changes, does the other variable also change? How does the variable change?
* Positive, negative, curvilinear
No manipulation of any variables
What do you use when examining the relationship by comparing scores for each group? (3)
1) Non-experimental research
2) Quasi-experimental
3) Experimental
What is non-experimental research? (3)
- One variable has two levels/conditions
- Lacks a control group
- No manipulation
What is experimental research?
*Establish cause-and-effect relationships
* Compare 2 or more groups on a dependent variable
* The group is manipulated
* Individuals are randomly assigned to the group
* Has a control group
What is quasi-experimental research?
*Similar to experimental
* Has a control group
* But groups cannot be randomly assigned
* In part because of preexisting participant/subject variable
* Does not provide a definitive answer about cause-effect
Difference quasi-experimental vs experimental
Quasi cannot be randomly assigned.
What are the two types of validity and their subgroup?
-Validity of measurement: face validity and construct validity.
-Validity of experiment: Internal validity and external validity
What is internal validity?
The extent to which the observed results represent the truth in the population we are studying.
What is external validity?
How well the outcome of a research study can be expected to apply to other settings.
Validity in nonexperimental research strategies?
- Nonexperimental research allows the researcher to examine the behavior in real-life settings
- Realistic environments offer higher external validity
- Environment is not manipulated or controlled ∴ limited internal validity
Validity in Experimental Research Strategies?
- Experimental research allows careful control of the environment
- Conducted in a controlled and constant lab setting ∴ high internal validity
- Experimental research often conducted in unfamiliar
environments, so harder to generalize beyond the experimental setting ∴ limits external validity