Types of samples

What is a sample

A sample is a subset of a population selected for measurement or observation in statistical analysis. It is used to make inferences about the larger group from which it is drawn.

A simple random sample

every member of the population is equally likely to get selected

Ways to srs

Ways to srs; number each person in the population 1-n and place numbered cards in the hat and randomly select the numbers, or use a random number generator.

Stratified sample

A sampling method where the population is divided into subgroups, or strata, and random samples are taken from each strata to ensure representation. —-members of the stratified have similar characteristics

cluster sample

A sampling method where the population is divided into clusters, typically geographically. The members of the clusters of do not have similar characteristics

 imagine we want to take a sample of small business owners in a large city, we can use zipcodes and survey two or three of them… but it doesnt always represent the whole population

systematic sample

 is where everyone in the population is assigned a number, and the researchers select a random number from the sample. The members of a population are selected at regular intervals from a randomly selected starting point. This method aims to provide a representative sample without the need for identifying subgroups.

convenience sample

a researcher gets members of a population that are easy to get and are convenient

homogenous groups

are subgroups in a population that share similar characteristics, often making it easier to analyze specific traits or behaviors among them.

heterogeneous groups

are subgroups in a population that have diverse characteristics, making analysis of specific traits or behaviors more complex.

double blind

oth researchers and participants are blind to crucial aspects of the study…Both do not know who is receiving the treatment, reducing biases as a result

single blind

only one of the two groups are blind and do not know which group is receiving which, helping to reduce biasness

control group

serves as a baseline for the data to see if the treatment is effective

experimental group

receives the treatment or intervention being tested in a study, allowing researchers to evaluate the effect of the treatment compared to the control group.

placebo group

receives the non-real treatment(like a sugar pill) allowing for comparison to evaluate the actual effects of the treatment by understanding expectations and psychological effects.

confounding variable

is a variable that is related to the explanatory variable and influences the response variable and makes it challenging to determine cause and effect

What should a well-designed experiment include (4)

1. comparisons

2. Random assignment

3. Replication

4. control

What is a comparison in an experiment

of at least two treatment groups, where one should at least be a control

What is a random assignment in an experiment

random assignment of treatments in the experimental groups

What is a replication in an experiment

enough experimental groups to detect a difference in treatments

What is a control in an experiment

a standard against which experimental outcomes are compared, representing the absence of a treatment and control of confounding variables.