AP Stats Unit 4 vocab

Convenience Sample

Selecting a sample of individuals who are easy to talk to

• ex. big bang on 4th floor

• bad

Voluntary Response Sample

Respondents choose to respond

• those likely to respond are those with strong opinions

• ex. dashathon and parents

• bad

Simple Random Sample (SRS)

Occurs when each individual in the population has an equal chance of being selected

Bias

occurs when using a poor sampling method

• typically over or under estimates the actual data

Stratified Random Sampling

Classifying your population into strata (groups w/similar characteristics)

• srs within each strata to create a sample

• ex. bell schedule

  • strata: classes

  • Select: 10 of each class

Cluster sampling

smaller groups that represent the population

• “clusters”

• ex. Dasher Dens

Undercoverage

occurs when some members of the population cannot be chose for the sample. Occurs before the sample is taken

Nonresponse

Those chosen either refuse or cannot participate. Occurs after the sample is taken

Response Bias

Responses are incorrect in some way (lying)

Wording of Questions

leading Q’s, big vocab, or confusing phrasing that may lead to bias

Observational Study

observes individuals and measures variables of interest but does not attempt to influence the response

Experiment

Deliberately imposing some treatment on individuals to measure their response

Lurking Variable

a variable not among the explanatory or response variables in a study but might influence the response variable

Confounding

occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other.

Treatment

a specific condition applied to the individuals in an experiment

• if the experiment has several explanatory variables, this is a combination of specific values of these variables

Experimental units

the smallest collection of individuals to which treatments are applied

subjects

when the units are human beings they are called _____

What are the 4 principles of Experimental Design?

Comparison, Control, Random Assignment, Replication

Comparison

two or more treatment groups - help avoid lurking variables

control

keeping variables that might impact the response the same for all treatment groups

Random assignment

randomly assigning indiv. to treatment groups

Replication

must have ample amount of subjects. If possible repeat the experiment

Placebo Affect

Response to a dummy variable

Double blind Experiment

Neither the subjects or those administrating treatments know which subjects are receiving which treatments.

Statistically Significant

An observed difference so large it would be unlikely to occur by chance -or- The likelihood that our result was caused by something other than random chance

Blocking

a group of individuals known before the experiment to be similar in some way which will influence the results

Matched Pairs design

blocks size 2 (similar individuals) -or- one individual receives both treatments.