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Stack #56283
| Question | Answer |
|---|---|
| population | an entire group of individuals |
| census | involves using every member of a population |
| sampling error/sampling variability | involves the natural variation one would expect to see in sample statistics from sample to sample |
| sample | a subgroup of a population |
| sampling techniques | voluntary response sample, convenience sample, simple random sample, stratified random sample, multistage sample design, systematic sample, cluster sample, |
| voluntary response sample | consists of peopel who choose tobe part of a sample by responding to a genearl appeal BIAS |
| convenience sample | invovles choosing the most convenient individuals from the population for your sample BIAS |
| simple random sample | (unbaised) a sample of size n selected in such a way that every set of n individuals has an equal chance of benig selected for the sample |
| stratified random sample | a) divide population into stratas b) choose a separate srs for each strata c) combine all of those individuals chosen from all of the stratus to make up the full sample |
| strata | groups of similar individuals |
| multiple sample design | see exmplae |
| systematic sample | suppose you want to insopect packages of potato chips coming off the lays factory assembly line. a systematic sample would involev inspecting, for exmpla,e every 25 bag |
| cluster sample | an srs from a set of all designated clusters-- suppose youwant to examine 10th gade MCAS scores from various high schjools instead of compliing a list of individual students, select high schoolsand examine scores from students in these schools |
| a probability sample | gives each member of the population a known chance to be selected |
| undercoverage | occurs when some groups in the population are left out of the process of choosing the sample (the population is not the same group as the sample frame) |
| sampling frame | the grou[ from which the sample is chosen |
| nonresponse | occurs when an individual chosen for the sample cannot be contacted or refuse to cooperate |
| response bias | occurs wehn an indvidiaul in a sample chooses an answer to a survery that she/he thinks is the best rather than the truth |
| wording of question | may influence a person by leading the individual being question to one answe as opposed to anothw |
| an observationalo study | observes individuals and measures variables of interest but does not atempt to influence the response |
| an experiment | deliberty imposes some treatment on indviduals in order to observe their responses. an experiment can help elinminate lurking variables |
| experimental iunits | individuals on which the experiment is being done. if the units are people they are called subjects |
| treatment | the speicifc experimental condition applied to the units. the level of treatment is measured by the expklanatory variable and the level of the variable we're intersted in is measured by the response variavle |
| factors | the explanatory variables in an experiemnt. |
| 3 basic principles of experimental design | control, randomization, and replication |
| control | the effect of lurking variables on the response variable. it is importan to know that the changes in the response variable are due tot he explanatory variable and not some other variable not involved in the study |
| control group | commonly given a placebo instead of the treatment being studied |
| comparison group | for example, coming new and improved cearel to waht is currently on the market |
| randomization | ensures tht the individuals are assigned to the treatment groups by chance |
| replication | of the experiment many times or on many subjects ensures that the erspuslts are not just due to chance variation |
| an experiemnt that has randoma ssignment and a control or comparison group is called | randomized comparative experiemtn |
| an observed effect too large to attribute plausible to cahnce is called | statistically significant |
| the placebo effect occurs when a subject | receiving a placebo reacts favorable to it |
| an experiment is blind if | the subejcts int he study do not know which treatment they are receiving |
| an experiment is double blind | if neither the experimenter or the subcejts know who is receving which treatment |
| a block | is a group of experimental units or subjects that are knwion before the experiment to be similar in some way that is expected to affect the ersponse to the treatments. |
| block design | the random assigment of units to treatments that is carried out separatley within each block |
| matched pairs design | a- subecjts are matched with themselves and given twodiffernt treatments or b- simlar subecjts are matched and each assigned a difent treamtnet |
| the initation of ahcen behvaor, based on amodel that accurately refelcts the expemetn is | simulation |