Term

Definition
With a census, the whole population is sampled, versus a portion of the pop'n 


Term
Why is taking a census too difficult 

Definition
time, expense, tedious, impractical, need proper participation and volunteering, and we sacrifice quality for quantity. 


Term
What are the three stages to sampling? 

Definition
1. Determine who/what to sample 2. Determine how you're going to choose these subjects 3. Determine how many you'll need to be confident in your findings 


Term
Your test subjects must be _____ ___________ of your population of interest 

Definition


Term
Give an example of inclusion and exclusion criteria 

Definition
Inclusion: Selecting individuals who you want/need to study/observe Exclusion: ruling out individuals who would confound the study results 


Term
What are the different population types as we go from what we want to test, to what we actually study? 

Definition
Target Population Source Population Sampling Frame Sampling Units Study Population 


Term
What the broad types of sampling strategies in Epidemiology? 

Definition
Nonprobability, Probability, and Others (either non or probability) 


Term
What are the types of Probability Sampling? 

Definition
Simple Random Sampling Systemic Random Sampling Stratified Random Sampling Cluster Sampling Multistage Sampling 


Term
What are the types of Nonprobability sampling? 

Definition
Convenience Judgment Purposive 


Term
What is Convenience sampling? 

Definition
Sampling units are chosen b/c they're easy to get 


Term
What is judgment sampling? 

Definition
the investigator chooses what he or she deems to be representative of the population 


Term
What is Purposive sampling? 

Definition
Sampling units are chosen on purpose because of their exposure or disease status 


Term
T or F: Nonprobability sampling is a bad method 

Definition
false! It is good, it just needs caution  can produce biased results if the subjects you select are not representative of the target population 


Term
What are the pros to doing nonprobability sampling? 

Definition
 relatively easy  can be cheaper if you choose subjects based on convenience  appropriate for homogenous population 


Term
In simple random sampling, it is required that the _____ _____ is known 

Definition


Term
T or F: In SRS, all individuals have an equal chance of being included 

Definition


Term
How does systematic random sampling work? 

Definition
A sampling interval (say, every 5 cows) is computed, and the starting point is selected on a formal random basis.
Then, simple or systematic random sampling is conducted within each strata 


Term
T or F: In St.R.S., the percentage sampled in each strata must be the same in all groups 

Definition


Term
How does stratified random sampling work? 

Definition
The sampling frame is broken into groups (strata) based on some factor that is likely to influence the level of the characteristic being measured.
Then, simple or systematic random sampling is conducted within each strata 


Term
What is cluster sampling? 

Definition
The sampling unit is a group of individuals with things in common (herd, household, geographic region, etc.) BUT  the unit of concern is still the individual 


Term
T or F: Cluster sampling may be probability or nonprobability 

Definition


Term
T or F: In cluster sampling, not all the sampling units are tested 

Definition


Term
When is multistage sampling convenient? 

Definition
 When there are too many individuals ina cluster to obtain measurements on  when the individuals in a cluster are so alike that measuring just a few will provide sufficient info  if sampling is done randomly, it can be more cost efficient than other probability sampling meathods 


Term
What is multistage sampling? 

Definition
Similar to cluster sampling, though sampling takes place at the cluster/group level as well as the individual level. (i.e. first sample random groups, then randomly sample individuals from each of those groups) 


Term
Main difference between multistage and cluster sampling? 

Definition
Multistage: Selection occurs at two levels, and only a proportion of individuals are selected and measured
Cluster: All individuals in each group are selected and measured 


Term
What is the sampling unit in cluster sampling? 

Definition
The group of individuals (the herd, the barn, etc) 


Term
What is the unit of concern in cluster sampling? 

Definition
The individual (i.e. cow, child, etc.) 


Term

Definition
It is how tight your CI is around your study mean/proportion 


Term
On what does precision depend? 

Definition
Sample size, variability of characteristics, and sampling strategy used. 


Term
What does a smaller CI say about the precision 

Definition
A smaller is range is more precise, and therefore better 


Term
How do you calculate sample size for estimating simple characteristics? 

Definition
1. Estimate variance 2. Select level of confidence that your estimate will include the true value in the population 3. Specify desired precision 4. Use appropriate formula 


Term

Definition
The variance (of proportions) where p = diseased inds where q = nondiseased inds
(p = 1q) 


Term
what is the variance of the means? 

Definition


Term
What is the Zvalue for a 95% confidence interval? 

Definition
1.96 (for a twosided hypothesis) 


Term
What is another way to describe precision? 

Definition


Term
In a descriptive study, why do we calculate sample size? 

Definition
To estimate the mean or a proportion (different equations) 


Term
If you decrease the allowable margin of error, what will happen to the size of the sample that you require? 

Definition
It will drastically increase 


Term
How do you calculate sample size in analytic observational studies? 

Definition
1. State null & either 1 or 2sided alternative hypothesis 2. Determine what it is you're comparing 3. Determine how much of a difference b/w the groups you want to detect and if necessary, the expected variance 4.Set alpha and beta (confidence and power) 5. Use the appropriate formula or table (based on what you're comparing) to estimate sample size 


Term

Definition
(P) The ability of a test to detect differences between groups when a real difference exists 


Term
What is a commonly used power, and what is the Zvalue? 

Definition
80% power, beta = 0.2
Z(0.2) = 0.84 


Term

Definition
When we reject the null, given that it's true 


Term

Definition
When we don't reject the null, given that it's false 


Term
What is the probability of making a type 1 error? 

Definition


Term
What is the probability of making a type 2 error? 

Definition


Term

Definition


Term
What is a twp sided hypothesis? 

Definition
When you predict that a value can either be higher or lower in one group over another 


Term
As the size of the difference between 2 means or proportions decreases, the required sample size.... 

Definition


Term
As the level of power desired to detect a difference between the two groups increases, the required sample size.... 

Definition


Term
As the number of confounders you're controlling for increases, the required sample size.... 

Definition


Term
As the number of hypotheses tested increases, the required sample size.... 

Definition


Term
What is a better method of representing the population that you want to characterize, prob sampling or nonprob sampling? 

Definition
Prob sampling, though it may not always be practical or possible 


Term
What is required to calculate an appropriate sample size? 

Definition
 desired precision of your estimate  expected variation in the data  (in analytical studies) the size of difference you want to detect b/w groups; and the desired power 

