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STATS quiz c4-6
zSTATS quiz c4-6
| Question | Answer |
|---|---|
| how sample surveys go wrong | confidence statements dont reflect all sources of error that are present in practical sampling |
| sampling errors | errors caused by the act of taking a sample, how we chose the sample - causes results in a sample to be different than census results |
| random sampling error | deviation between sample's statistic and the population's parameter being CAUSED BY CHANCE when selecting sample |
| what does MOE influde | only includes random sampling error |
| nonsampling errors | not related to how we collected sample, there was no mistake made in method of choosing -can even be present in a census |
| examples of bad sampling methods | convenience sample, voluntary response, undercoverage |
| convenience sample | selecting individuals that are easiest to reach/contact |
| voluntary response | sample chooses itself -people with strong opinions are likely to put in a response |
| undercoverage | routinely leaving people (a certain group) out of a sample. |
| examples of nonsampling errors | processing errors, poorly worded questions, response error, nonresponse error |
| processing error | mistakes in date entry or arithmetic |
| poorly worded questions | question is slanted to favor one response over another |
| response error | inaccurate responses due to lying, bad memory, etc. |
| nonresponse error | failure to obtain data from an individual in a sample |
| does a NONsampling error effect MOE | no, only random sampling error |
| statistical methods to correct error | strata, cluster sapling, systematic sampling |
| strata | sampling done in stages/layers. typically a representative setup. -can take away RANDOMNESS |
| example of strata | if choosing 1/4 of each grade, after getting 250 freshman, the rest of the freshmen don't have an equal chance anymore -takes away randomness |
| cluster samples | sampling in groups based on location (geographical) -not always random |
| systematic sampling | selecting every (n)th individual |
| explanatory variable | the variable that we think explains or causes changes in the response variable -independant |
| response variable | the variable that measures an outcome/result -dependent |
| treatment | any specific experimental condition applied to a subject |
| observational study | passively collected data, no treatment is imposed -no intervening |
| experiment | intentionally intervening with subject by imposing some treatment in order to investigate the impact on the response variables |
| lurking variable | not one of the known explanatory variables, has important effect on response variable -causes trouble when trying to estimate a cause and effect relationship between explanatory and response variables |
| confounded variable | when effects on response variable cant be distinguished from eachother |
| placebo | treatment that has no active ingredient. individuals respond favorably -can be confounded with the effect of treatment |
| double blind | neither the subject or researchers know who received what treatment |
| random comparative experiment | we compare 2 or more treatments, use chance to assign treatment/subject, use enough subjects so effects of chance are small/not likely |
| randomization | using IMPERSONAL chance in assigning. produces groups of subjects that should be similar, on average, ina all respects before treatment is applied |
| comparative design | exposes all groups to similar conditions, other than the treatments they receive. this ensures that any lurking variable operates equally on all groups and, on average groups differ only in treatment given |
| comparative design: chance or not chance | not due to chance |
| control | we want to ______ the effects of lurking variables on response, most simply by comparing 2 or more treatments |
| statistical significance | an observed effect of size that would rarely occur by chance. |
| matched pairs design | compares just two treatments on subjects who are matched based on similarity |
| block design | a group of experimental subjects that are known before the experiment to be similar in some way that is expected to affect the response to the treatments |
Created by:
liz gelles