Statistical Methods STA 2023
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This 2 page Study Guide was uploaded by Winnifred Macejkovic on Thursday October 29, 2015. The Study Guide belongs to STA 2023 at Valencia College taught by Patrick Murphy in Fall. Since its upload, it has received 40 views. For similar materials see /class/231202/sta-2023-valencia-college in Statistics at Valencia College.
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Date Created: 10/29/15
SURVEYS AND STUDY DESIG e A subset ofthe populataon O Populatron All measurements or obseryatrons ofrnterest Sampl GO popul ata on s ampl es Blas The desrgn of a study ls blasedlflt systemataeally favors eertatn outeomes Any phng meth systematre fallul39e ofa sam odto represent rts populataon ls blas EIAS m smwws nvenlenee Sample Sampllng only those lnddvlduals who are eonyenrently avallable annnteer respnnse When lndmduals ean ehoose for themselves whether ornot ey Nnnrespnnse When alarge portaon ofthose sampled falls to respond thng m a suryey deslgn that ln uences responses Underenverage Sampllng that glves part of a populataon less representataon than rt has m the populatron SAMPLING mamas SRS Simple Randnm Sample A Slmple Random Sample ofslze n eonsrsts of n lnddvlduals from the populatron ehosen m sueh away that every grou o n lnddvlduals from the populataon has an equal ehanee to be the sample aetually las ystema c chooslng eyery 1t lnddvldual For example seleetrng the 50mpan off of an assembly hne to eheek for quahty Stratified The populatron ls partataonedrnto subgroups ealled stmta andthen random samples are drawn f 211 Cluster The populataon ls partrtroned rnto subgroups ealled clusters andthen a andom sam le of elusters are seleeted lnformatron from Everylnddvldual ar e 52121201 elusters Multistage uslng a eombrnatron ofstxanfled eluster andor systematre sampllng mques Observational Study Observeswatches individuals and measures variables of interest but does not attempt to in uence the responses NO treatment Experiment Deliberately imposes some treatment condition in order to observe the responses Experimental units Individuals involved in the experiment Usually called subjects or participants when the individuals are human Do not confuse this with unit ofmeasure examples of which are mileshour degrees seconds etc Lurking variable A variable that has an important effect on the relationship among the variables in a study but is not included among the variables studied Sometimes called a Confounding variable THE PRINCIPLES OF EXPERIMENTAL DESIGN 0 Contr017Control the effects of lurking variables on the response most simply by comparing two or more treatments 0 RandomizationiThe use of impersonal change to assign experimental units to treatments In other words try to pick your samples randomly see SRS above 0 ReplicationiReplicate the experiment over as many subjects as possible In other words pick a large sample size Replication can also be interpreted as repeating the experiment on different samples from the population to ensure consistency in the results Placebo A fake treatment Placebo effect The tendency of many human subjects often 20 or more of participants to show a response even when administered a placebo In other wordsjust being involved in the experiment has caused a change in the response Control group The experimental units assigned to a baseline treatment level or no treatment at all such as with a placebo Double dummy Comparing two different treatments at once with corresponding placebos An example would be when subjects who want to quit smoking are broken up into two groups 0 Group linicotine patch placebo gum 0 Group Ziplacebo patch nicotine gum Blind The participant does not know which treatment is being given to each individual Double blind Neither the researcher nor the participant knows which treatment is being given to each individual
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