Biostats Flashcards
Purpose of probability sampling?
Used to generalize a population at large
Works toward representativeness of population
Nonprobabilty sampling uses what methods?
In what circumstances is it used?
Convenience, snowball, quota
It is used when probability sampling can’t be used
(Less generalizability toward whole population)
Parameter vs Statistic:
- Parameter
* Summary of a given variable in a population - Statistic
* Summary of a given variable in a sample
What do you have to remember to do in systematic sampling in order to insure the generated sample is random?
randomly select the start point where the interval will begin
Why is stratified sampling a good method when you are dealing with small sub-populations?
IT is useful because this technique allows for oversampling of small sub-populations to achieve necessary statistical power
What type of technique is being used in a survey sample where individuals are chosen randomly from specific states rather than the entire population?
Cluster sampling
Go down to cities within those states and you have multi-stage
What percent of values fall one standard deviation greater and less than the central mean in a normal curve?
68%
When using a 95% confidence level, what is your standard error?
1.96
What is alpha?
your confidence level, usually .05, which is a confidence level of 95%
How do you calculate stadnard error?
standard deviation divided by the square root of the number in your sample
What is the null hypothesis:
Assuming there really is “no difference” in the population, what are the odds of obtaining our particular sample finding?
We cannot “prove” the null hypothesis, we can only fail to reject it!
Type 1 Error
vs
Type 2 Error
Type 1 : Reject a true null hypothesis
Type 2 : Fail to reject a false null
