Chpt 1: Statistics and Samples Flashcards
What is a population?
All individuals in the world
What is a sample?
A subset of a population that we collect and analyze
What is a parameter?
Something that describes a population
Do we always know the parameters of a population?
No, but we can use estimates from samples to get a sense of a populations parameters
Are parameters fixed?
Yes, parameters are constant
Are estimates fixed?
No, they are random variables and change from one sample to the next within the same population
What is sampling bias?
When there is a systematic difference between estimates and parameters
What is sampling error?
When there is an undirected deviation of estimates away from parameters (sampling error is indicative of precision; the lower the sampling error, the higher the precision)
When does sampling bias arise?
When the sample is not truly representative of a population ex. The 1936 election results vs questionnaire results
What makes a good sample?
When each member of a population has an independent and equal chance of being selected
What are the two major types of variables?
Numeric and Categorical
What are the two types of numeric variables?
Discrete and Continuous
What is a discrete variable?
A variable that can only take some values ex. Age
What is a continuous variable?
A variable that can take any value ex. Core body temperature
What are the two types of categorical variables?
Ordinal and Nominal
What is an ordinal variable?
A variable that can be ranked ex. Snakebite severity scale
What is a nominal variable?
A variable that cannot be ranked ex. Sex chromosome genotype
What is the frequency distribution?
The number of times a value occurs in a sample
What is the probability distribution?
The proportion of the population with a value ( the real probability distribution of a population is almost never known, they are often estimated)
What is an experimental study?
When researchers assign treatments to individuals
What is an observational study?
When the researchers do not assign treatments to individuals
In which type of study can cause and effect or causation be proven?
Only in experimental studies, not in observational studies
What are confounds?
They are variables that are not considered in an experimental study and may potentially drive an association
