AP Stats unit 3-Experimental design

population

the entire group of indivi­duals we want inform­ation about

census

a complete count of the popula­tion; when you gather general inform­ation about the entire population

sample

a part of the population we actually examine in order to gather inform­ation

sampling design

the method used to choose the sample from the population

sampling frame

is a list or source that contains all the units (individuals, households, etc.) from which a sample will be selected. 

simple random sample

is a sampling method in which every member of the population has an equal chance of being selected.

stratified random sample

is a sampling method that divides the population into distinct subgroups (strata) based on shared characteristics and then randomly selects samples from each stratum, ensuring representation across the different subgroups.

systematic random sample

randomly select a number between one and n and survey every nth person after that.

cluster random sample

The population is divided into naturally occurring groups (clusters) that are often geographically based (e.g., schools, neighborhoods, hospitals). and then randomly selects entire clusters to sample, often used for convenience or cost-effectiveness.

multistage sample

is a sampling method that combines different sampling techniques, such as stratified and cluster sampling, at various stages to obtain a more representative sample from a larger population.

describe an srs

put the names/­numbers of all ___ on slips of paper and place in a hat. Mix and randomly draw ___ slips of paper without replac­ement. Survey the corres­ponding people.

describe a systematic random sample.

number all ___ and place ___ numbers in a hat. Mix and randomly select one number and survey the corres­ponding person. Survey every nth person on the list after that.

describe a cluster random design

number all clusters and put the numbers into a hat Mix and randomly select a number from the hat. Survey everyone in that cluster.

stratified random sample

sort everyone into strata then number ___ in all the stratum. place the numbers in a hat and draw __ numbers. survey the corres­ponding people in that specific stratum. repeat the process for all strata

Completely randomized design

experi­mental units are assigned completely at random to treatments.

randomized block design

experi­mental units are blocked in homoge­neous groups and then randomly assigned to treatmentswithin each block to control for variability.

matched pairs design

a special type of block design; match up experi­mental unit according to similar charac­ter­istics and randomly assign one to treatment A and the other get treatment B randomly.

observational study

a study where researchers observe subjects without manipulating anything; they collect data on variables of interest.

Experiment

actively impose a randomly assigned treatment in order to observe the response

experimental unit

the single individual to which the different treatments are randomly assigned

factor/ explanatory variable

what we test or what we change

Level

the specific values or settings of a factor in an experiment.

response variable

what you measure or record at the end of the experiment

treatment

a specific experi­mental condition applied to the units

Control group

a group that is used to compare the factor against; can be placebo

placebo

a "­dum­my" treatment that can have no physical effect; not required in every experiment

blinding

method used so that units or evaluators do not know which treatment units are getting

double blinding

neither the units nor the evaluators know which treatment a subject recieved.

confounding variable

a third variable that potent­ially affects both the factor and the response variable.

Randomized block design

completely randomized design