Elementary Terms
The official count of a population
Census
a subset of the population
Colors of cars in the parking lot
Nominal
People should brush their teeth at least twice a day for at least two minutes with each brushing. For a class project, you ask a random number of students at your school questions concerning their tooth-brushing habits
Survey
Ask the first 20 people seen carrying mineral water in a park on a summer day
Systematic
A characteristic of interest for the elements
Variable
A number that describes the whole population
Daily temperature in Ephrata, PA
Interval
The local Dept. of Transportation is responsible for maintaining lane and edge lines on its paved roads. There are two new paint products on the market. Twenty comparable stretches of road are identified. Paint A is randomly assigned to ten of the stretches of road and Paint B to the other ten. The department finds that Paint B lasts longer.
Observational Study
Ask your friends
Convenience Sampling
A science that consists of collecting, organizing, analyzing, and interpreting data
Statistics
The group in an experiment that does not receive the experimental treatment
Control Group
A restaurant rating (A, B, C, D, F)
Ordinal
The National Highway Traffic Safety Administration conducts annual studies on drivers' seatbelt use at a random selection of roadway sites in each state in the US. To determine if seatbelt usage has increased, data are analyzed over two successive years.
Observational Study
Student ID numbers are randomly selected by a computer for a survey of student opinions on college athletics.
Simple Random Sampling (SRS)
Using observations from a sample to draw conclusions about a population
Inferential Statistics/Inferencing
A zero that implies "none"
Inherent Zero
The amount of money spent at the War Memorial Field Burger Shack at last week's football game.
Ratio
A television network mails a questionnaire to randomly selected people across the country to determine whether they prefer watching sitcoms or dramas.
Part of the research plan calls for describing and comparing the opinions of four different ethnic groups. For a total sample of 300, the researcher selects 75 participants from each of the four predetermined subgroups.
Stratified Sampling
Repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances
Replication
Any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups
Blinding/Blinded
Nominal
An engineer is planning to test 50 metal samples to determine whether a new titanium alloy has a higher strength than a different alloy.
Experiment
A sample of 2,000 was sought to estimate the average achievement in science of fifth graders in a city’s public schools. The average fifth grade enrollment in the city’s elementary schools is 100 students. Thus, 20 schools were randomly selected and within each of those schools all fifth graders were tested.
Cluster Sampling