Sampling and Experimentation Flashcards
Population
The entire group of individuals or items of interest
Sampling Frame
A list of all members of the population
Sample
The part of the population that is being examined
Sample Survey
The process of collecting information from a smaple
Census
The process of collecting information from all units in a population
Observational Study
An activity in which the experimenter observes the relationship among variables rather than creating them
Experiment
A activity in which the experimenter applies treatments to subjects to see a relationship between variables
Confounding Factor
Occurs when the two variables of interest are related to a third variable instead of just to each other
Biased Sampling
Result in values that are systematically different from the population values or favor certain outcomes
Judgmental Sampling
Makes use of a nonrandom approach to determine which item of the population is to be selected in the sample
Sample of Convenience
A sample that is rather easy to obtain
Volunteer Samples
The subjects choose to be a part of the sample
Simple Random Sampling (SRS)
A process of obtaining a sample from a population in which each member has an equal chance of being selected
Types of Simple Random Samples
- Sampling with replacement from a finite population
2. Sampling without replacement from an infinite population
Systematic Sampling
The first item is selected at random from the first k items in the frame, and then every kth item is included in the sample
Stratified Random Sampling
The population is divided into groups called strata and a simple random sample is taken from each stratum
Proportional Sampling
The population is divided into groups called strata and a simple random sample of size proportional to the stratum size is selected from each stratum
Cluster Sampling
A population is divided into non-homogeneous groups called clusters and a simple random sample is obtained from some clusters but not all of them
Sampling Error
Variation inherent in any survey
Response Bias
Caused by the behavior of the interviewer or respondent
Non-response Bias
Occurs if the person selected for an interview cannot be contacted or refuses to answer
Under-coverage Bias
Occurs if part of the population is left out of the selection process
Wording Effect Bias
Occurs is confusing or leading questions are asked
Response/Dependent Variable
The variable to be measured in the experiment
Explanatory/Independent Variable
A variable that may explain the differences in responses
Experimental Unit
The smallest unit of the population to which the treatment is applied
Confounding Variable
A variable whose effect on the response cannot be separated from the effect of the explanatory variable
Factor
A variable whose effect on the response is of interest in the experiment
Levels
The values of a factor used in the experiment
Treatments
The factor-level combinations used in the experiment
Control Group
A group of experimental units similar to all the other experimental units except that it is not given any treatment
Placebo Group
A control group that receives a placebo in experiments involving medicines
Blinding Technique
Used in experiments to prevent bias
Single-Blind Experiment
Either the patient does not know which treatment they are receiving or the person measuring the patient’s reaction does not know which treatment was given
Double-Blind Experiment
Both the patient and the person measuring the patient’s reaction do not know which treatment the patient was given
Blocking
Used to control the effects of known factors
Block
A group of homogeneous experimental units
Replication
Refers to the process of giving a certain treatment numerous times in an experiment or of applying it to a number of different experimental units
