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Research Methods
Chapters 11 & 12
24
Other
Undergraduate 2
12/01/2009

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Term
Why Sample?
Definition
It allows us to accurately infer characteristics about a population. Its cheap and fast.
Term
What is a parameter
Definition
Data gathered from an entire population
Term
What is a sample?
Definition
A selection of events from a population
Term
What is a population?
Definition
A group defined by the researcher
Term
What is bias?
Definition
The tendency for a sample to be wrong so it doesn't represent the population accurately
Term
Essentials of sampling:
Definition
1) Must represent the population accurately. 2) Must be large enough to permit accurate analysis of the data they gather
Term
Sample size: how large should a sample be?
Definition
Depends on how much sampling error (bias) you are willing to tolerate
Term
Sampling error. what is it?
Definition
margin of error associated with the sample
Term
Confidence Interval
Definition
Good reporting of a survey has it. it is the % Chance its completely wrong
Term
Statistical effects of small samples
Definition
1) Small samples increase sampling error. 2) Small samples make it difficult to detect significant relationships
Term
Volunteer Subjects: The 4 problems with it
Definition
1) Increased need for social approval.
2) Increased socioeconomic status
3) Increased intelligence
4) Tend to have reduced conformity
Term
Random sampling
Definition
When each person in the population has an equal chance of being selected
Term
Periodic Sampling
Definition
True random sampling. Simple random sampling. Drawn at random. Not useful when subjects need to be divided into subgroups. used in field settings
Term
Stratified sampling
Definition
Random. use when stratified group things are wanted. Problems: Have to know the size of the strata to use the info. Uses large samples = $$
Term
Cluster samplng
Definition
A way around stratified sampling. Look for naturally occurring samples in the enviro.
Term
How do you sample clusters?
Definition
1) ID the clusters. 2) Draw random samples from the clusters.
Term
Convenience Samples
Definition
Non-random sampling. Use a selection of events that a readily available. EX: Teacher uses his/her students
Term
Quota sampling
Definition
Non-random. Similar to stratified, don't take random sample. EX: Only want to study people over 6 ft tall and compare to people >5ft. tall
Term
Snowball sampling
Definition
Used to study deviant (rare characteristic) behavior. Works well w/ naturally occurring events. 
Term
Disadvantages of snowball sampling
Definition
1) Yield biased results.
2) Statistically you can't compute the confidence interval. 3) Can't control the pop. 4) Refusal rate of over 25% then the info auto fails
Term
3 kinds of descriptive statistics
Definition
1) Averages ex: avg. GPA. 2) Variability ex: compares averages. 3) Correlations ex: looks to see relationships in variability
Term
Inferential Statistics
Definition
Use probabilities to make inferences about populations. ex: probability it will rain tomorrow.
Term
Measures of central tendency
Definition
Tell us whats going on in sample groups or pop's on the avg. EX: Mean, median, mode
Term
Measures of variability
Definition
Range, variance, standard deviation
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