Test 1 Flashcards
What is Simple Random Sampling?
List of all possible individuals in pop// randomly choosing n subjects in such a way that every set of n subjects has an equal chance of being selected for sample.
Pros of Simple random Sampling?
Convenient and easy.
Cons of Simple Random Sampling?
May not be representative of population.
ex: pop= 50% male and 50% female
sample= 75% male 25% female
What is Stratified Random Sampling?
The population is naturally divided into two or more groups of similar subjects, called strata.
What is an example of a Strata?
Strata 1= males
Strata 2= females
What do you do with each Stratum in Stratified Random Sampling?
Select simple random samples from each
What should the number from the Stratum correspond with?
The percentage of the total population in each stratum.
Pop= 60% male, 40% female
Sample= 200= 60% Male= 120
Female=40%=80
What is Multistage Random Sampling?
Because the population is naturally divided into groups we select several of these groups.
How does Multistage differ from Stratified?
Stratify samples some from every group, but Multistage only samples some groups, and each groups is further divided into subgroups.
What must happen to make it Multistage?
Must be at least two randomization stages.
Example of Multistage?
States= groups
1. randomly choose 5 states
2. randomnly choose 3 colleges from the state
3. randomly choose three courses at those colleges.
4. choose 5 students from within those 45 courses.
sample=225
Advantage of Multistage?
Less time intensive and costly
Disadvantage of multistage?
Might not be completely representative of the pop as a whole and probably will have bias.
What is the significance of designing and carrying out an experiment?
allows us to evaluate the effect of a treatment or treatments.
What are Experimental units?
The subjects measured
What is The Treatment?
An experimental condition applied to the experimental units
What is a Response?
The characteristic that is measured on experimental units.
What is a Comparison?
Wanting to compare results of one group w/ another.
What are Treatment Groups?
Groups (of experimental units) who receive the treatment(s).
What is a Control Group?
Group of experimental units who receive fake or no treatment.
What is a Placebo?
Fake treatment given to control group to prevent subjects knowing which group they belong.
What is Replication?
Each group should contain more than one subject for variation of result and reduce fluke occurrences.
What is Randomization?
Subjects should be randomly selected and randomly assigned to different groups.
What is Blinding?
Subjects should not know which group they belong to.
What is Double-Blinding?
Those in contact w/ subjects should also not know which group they belong to.
What is Bias?
Anything that systematically favors some outcomes over others and which would cause us to question the truth of results.
What is Confounding?
some factor other than treatment that makes treatment and control group different.
What is a Controlled Experiment?
The experimenter randomly selects experimental units to be in the experiment and can control to which each group is assigned.
What are the two necessary conditions to be a controlled experiment?
- experimenter has ability to impose treatments and placebo
2. experimenter has ability to compare results
What are controlled experiments often?
Double-blind, involve replication, and randomization, and are mostly free of bias and confounding.
What is an Observational Studies?
The experimenter observes the experimental units as they are.
In observational studies how does the experimenter control which group each subject is assigned?
The experimenter cannot or does not control that
What does the experimenter not do in Observational studies?
Do not impose treatments or placebo on experimental units.
