Statistics Sampling Review

sampling

studying part of a group to gain information about the entire group

voluntary response sample

a large group is invited to respond, those who respond are in the sample

experiment

a treatment is imposed on a subject and a response is observed

statistical inference

provides ways to answer questions, guaranteeing that the answers are accurate

population

the group that is sought to be learned about

sample

a subset of the population

convenience sampling

choosing a sample of people easy to reach

bias

a systemic failure of a sample to represent a population

simple random sample

every subject has an equal chance of being picked for the sample next

observational study

observes individuals and measures variables of interest, but doesn’t try to influence results

experimental units

individuals on which an experiment is performed

factors

explanatory variables

placebo effect

response to any treatment with a dummy treatment because an outcome was expected

control

treatments must be compared

randomization

randomly assigning subjects to treatment groups

completely randomized experimental design

all experimental units are randomly allocated among each treatment

statistically significant

an observed effect too large to be attributed to chance

replication

repeating each treatment on a large number of subjects to show systemic effects of the treatment

3 principles of statistical design

control, randomization, replication

hidden bias

not all experimental units are treated the same

double blind

subjects and people with whom they interact shouldn’t know what treatment they got

blocking

dividing subjects into groups that share similar characteristics

matched pairs design

one person gets both treatments, or similar people are matched and each gets a different treatment

stratified random sample

population is seperated into groups, and then people are taken from each group

systematic random sample

every nth subject

multistage sample

cluster sample

groups of people are chosen at a time