STATS (BIOL 243) FALL 2024

sample unit sample observation unit statistical population population of interest

the unit being selected at random, it may be the same as the observation unit or contain multiple observation unit

collection of the sampling units

scale of data collection, subject of study

collection of all sampling units that could have been in your sample, and represents the true scale in which your statistical conclusions are valid

collection of sampling units that you hope to draw conclusion about scope of the research question ideally the same as your statistical population

what we want to know/measure about the observation unit

scale

set of tools used to describe data

uses information from the sample to make a probolistic statement about the statistical population

descriptive stats are repeated for each group but inferential stats are only done once and can be used to make statements about the differences between groups

• all sample units have a probability of being included • selection of sampling units must be unbiased • selection of sampling units are independent • each possible sample has an equal chance of being selected

• researchers have no control over the variables • it characterizes something about an existing statistical pop • a tool for discovering associations, but can not make statements about the involvement of the sampling unit (cannot establish causation cause there is no way to know if the the factor is governed by something else

variable the investigators are interested in

variable that the investigator believes may explain the response variable

unobserved variables that affect the response variable

starts by identifying every sampling unit in the statistical population and then selecting a random subset of those to be in your sample. Each sampling unit has the same probability of being included in your sample.

used when the statistical population has some grouping (strata)

observation units are contained within a larger group that we can randomly sample (geographicl or organizational)

when there is a known outcome we are trying to explain

select a sampling unit, follow them through time to see if they developed the result we want

studies where the results are already known ie. case control studies

outcome is not yet known ie. cohort studies