Levels of Measurement
Species of fish caught: perch, bass, pike, trout
Nominal
A numerical representation of a real world phenomenon
Simulation
Population of all undergraduate college students: freshman, sophomore, junior, senior
Stratified
Observations and measurements of individuals are conducted in a way that doesn't change the response or the variable being measured
Observational study
This is a potential pitfall in surveys where words can have different meanings to different people
Vague wording
Guidebook rating of fishing area: poor, fair, good
Ordinal
The result of poor sample design, sloppy data collection, faulty measuring instruments, bias, etc.
Have 100 people line up and select every 5th person
Systematic
A treatment is deliberately imposed on the individuals in order to observe a possible change in the response or variable being measured
Experiment
A variable such as age, income, weight, height, etc.
Quantitative
Cost of rod and reel
Ratio
The study of how to collect, organize, analyze, and interpret numerical information from data
Statistics
Standing in front of a football stadium to ask people what their favorite sport is
Occurs when a subject receives no treatment but (incorrectly) believes he or she is in fact receiving treatment and respond favorably
Placebo effect
Using information from a sample to draw conclusions regarding the population
Inferential statistics
Time of return home
Interval
Omitting populations members from the sample frame
Undercoverage
In a survey of school children in a large city, randomly select five schools and include all children in each selected school
Cluster
A group that receives a dummy treatment, enabling the researchers to control for the placebo effect
Control group
A list of individuals from which a sample is actually selected
Sampling frame
Temperature of water throughout an 8 hour fishing trip
Interval
Measurements or observations from the entire population are used
Census
Use a variety of sampling methods to create successively smaller groups at each stage. The final sample consists of clusters
Cluster sampling
A group of individuals sharing some common features that might affect the treatment
Block
Confounding variables