Unit 5: Sampling and Experimentation

Observational Study

Observational Study

________: An activity in which the experimenter observes the reaction among variables rather than creating them.

Census

________: Process of collecting information from all the units in a population.

Replication

________: refers to the process of giving a certain treatment numerous times in an experiment, or even repeating an experiment multiple times.

Frame

________: List of members from which the sample is to be taken.

Independent

________ or explanatory variable: A variable that may explain the differences in responses.

technique

Blinding ________: used in medical experiments to prevent such a bias.

Factor

________: A variable whose effect on the response is of interest in the experiment.

Randomization

________: used to average the effects of extraneous factors on responses.

Sample

________: The part of the population that is actually studied.

Population

________: The entire group of individuals or things that we are interested in.

Experimental Unit

________: This is the smallest unit of the population to which treatment is applied.

Block

________: A group of homogeneous experimental units.

blind experiment

Double- ________: both the patient and the person measuring the patients reaction do not know which treatment the patient was given.

Response bias

________: when answers on a survey do not reflect the true feelings of the respondent.

Sample survey

________: The process of collecting information from a sample.

Nonresponse bias

________: when individuals selected to be in the sample who do not respond to a survey have different opinions from those who do.

Population

The entire group of individuals or things that we are interested in

Sample

The part of the population that is actually studied

Frame

List of members from which the sample is to be taken

Sample survey

The process of collecting information from a sample

Census

Process of collecting information from all the units in a population

Experiment

Planned activity that results in measurements

Observational Study

An activity in which the experimenter observes the reaction among variables rather than creating them

Biased sampling

methods result in values that are systematically different from the population values or systematically favor certain outcomes

Simple random sample

A sample of n subjects selected in such a way that every possible sample of the same size n has the same chance of being chosen

Systematic sample

A sample in which the researcher selects some starting point and then selects every kth element in the population

Stratified sample

A sample in which the researcher subdivides the population into at least two different subgroups (or strata), and then draws a sample from each subgroup

Cluster sample

A sample in which the researcher first divides the population into sections (or clusters), and then randomly selects all members from some of those clusters

Convenience sample

A sample in which the researcher simply uses results that are very easy to get

Sampling bias

the technique used to obtain the individuals to be in the sample tends to favor one part of the population over another

Nonresponse bias

when individuals selected to be in the sample who do not respond to a survey have different opinions from those who do

Response bias

when answers on a survey do not reflect the true feelings of the respondent

Dependent or response variable

The variable to be measured in the experiment

Independent or explanatory variable

A variable that may explain the differences in responses

Experimental Unit

This is the smallest unit of the population to which 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

Control group

Group of experimental units similar to all the other experimental units except that it is not given any treatment

Placebo group

The control group receives a treatment that looks and feels similar to an experimental treatment but is expected to have no effect

Blinding technique

used in medical experiments to prevent such a bias

Single blind experiment

either the patient does not know which treatment he or she is receiving or the person measuring the patients reaction does not know which treatment is given

Double-blind experiment

both the patient and the person measuring the patients reaction do not know which treatment the patient was given

Randomization

used to average the effects of extraneous factors on responses

Block

A group of homogeneous experimental units

Replication

refers to the process of giving a certain treatment numerous times in an experiment, or even repeating an experiment multiple times

Completely randomized design

treatments are assigned randomly to all experimental units or experimental units are assigned randomly to all treatments

Randomized block design

All experiments are grouped by certain characteristics to form homogeneous blocks, and then a completely randomized design is applied within each block

Matched-pairs design

An experimental design where participants in each condition of the experiment are matched according to important variables