stats 151 gathering data module 1

simple random sample

just random people picked to sample

stratified random sampling

strategy to choosing (choosing from specific groups like gender, age, race)

systematic random sampling

selecting a (k)th individual from a population where k is a constant (eg. 100 student but pick every 10th student)

cluster random sampling

selecting based on cluster (eg, geographical) and then surveying the entirety of the cluster

convenience sampling

surveying based off convenience (eg. surveying the first 10 people to walk into a grocery store instead of at random)

observational studies

researcher obsess and records info without intervening

key characteristics of observational studies

• no intervention

• observing specific traits

• natural setting

• causality limitation

experiments

involves intervention by the researcher

key characteristics of experiments

• treatment application

• controlled env

• randomization

causal inference

determine if an intervention actively changes an outcome

population inference

sampling a smaller group first then moving onto population

prospective studies

collect data as events moving in real time

retrospective studies

looking back on the past to gather and collect data

discrete quantitative value

a value with no decimals

categorical variable

categories have no numerical value but can ascend and descend

qualitative variable

more so group categories rather than a number value

numerical variables

ex. percentages

continuous quantitative variables

any value within a range

nominal qualitative variables

no inherent order eg eye colour

ordinal qualitative variable

order makes sense (eg. letter grades)

ordinal variable

used to rank or order data, the order has to have meaning, but never assume equal spacing between ranks

interval variable

no natural zero