Module 0 Flashcards
What is a Census?
A special sample that includes everyone and samples the entire population
What are the Cons to a Census?
Too expensive
Undercoverage
Too time consuming
What do people prefer to collect instead of a Census?
A sample
What are Statistics?
Summaries that are found from data in a sample
What are the two conclusions that a researcher can make with sample statistics?
Population Inferences
Causal (Cause and effect) Inferences
When are we allowed to make Population Inferences?
In statistics when we have random sampling
What does Randomization do?
Helps to eliminate the effect of unknown extraneous factors
What does Non-Random sampling lead to?
Biased results
What can we do with a non-random sample with Statistics?
The conclusions should be restricted to the sample and cannot be generalized to anyone else
What are the types of Random Sampling methods?
Simple Random Sampling (SRS)
Stratified Random Sampling
Systematic Random Sampling
Cluster Random Sampling
What is Simple Random Sampling?
SRS of each size n: each sample size n in the population has the same chance of being selected. E.x. Put all the names of the individuals in a population in a box and draw names to complete the sample
What is Sampling Variability?
Sample-to-Sample differences that occur in random sampling
What is Stratified Random Sampling?
The population is divided into different homogenous groups called Strata then simple random sampling is taken from each stratum. E.x. Dividing into provinces and then selecting some from each province
What is Systematic Random Sampling?
Starting from a randomly selected individual and selecting every Kth person. E.x. Standing at a booth and asking every 5th person that asks
What is Cluster Random Sampling?
Splitting the population into groups and then selecting one or a few groups and performing a census within each of them. E.x. A store owner who selects two departments out of all to get a statistics
What is Bias?
The tendency for a sample to differ from the corresponding sample in some systemic way
What are the 4 sources of Bias?
Selection Bias (undercoverage)
Response Bias
Voluntary Response Bias
Non-Response Bias
What is Selection Bias?
When some proportion of the population is not sampled or has a smaller representation than it has in the population
Ex. Inmates or people without addresses
What is Response Bias?
Refers to anything in the survey design that influences responses
E.x. Respondents may lie especially if asked about illegal or unpopular behaviour
What is Voluntary Response Bias?
Occurs when individuals can choose on their own weather to participate in the sample. E.x. An internet pill asking people how they feel about the healthcare system
What is Nonresponse Bias?
Occurs when a large population of those sampled fail to respond
E.x. Telephone survey is conducted to observe the eating habits of office workers but those who are selected are randomly away on vacation
When can we make Causal (cause and effect) Inferences?
When we have random allocation of the people to different conditions
What are Lurking variables?
Variables that are related to both group membership and to the that could possibly explain the result
What are the Study Designs?
Observation Studies
Randomized Experiment
What is an Observational Study?
When investigators observe individuals and measure variables but do not attempt to influence the responses. E.x. Studying the impact of distance of home to power plant on cancer incidence. The researcher did not assign houses they simply observed the data
What is a Retrospective Study?
A study that compares conditions after they have been unfolded
What is a Prospective Study?
A study that compares conditions as they unfold
What can be determined from Observational Studies?
Possible relationships but it is not possible for them to demonstrate Causal Relationships
What can be determined from Randomized Experiments?
Causal (cause and effect) relationships
What does a Randomized Experiment do?
Manipulates factor levels to create treatments
Randomly assigns subjects to treatments
Compares responses to treatments across groups
What is Random Allocation?
Randomly assigning subjects to certain groups in an experiment
