Review question:To estimate the proportion of students who support a smoke-free campus, you compute the proportion that say yes after responding to an email sent to all students asking “Do you support a smoke-free campus?” The data collected isA. Not biasedB. Biased because of wording biasC. Biased because asked over email instead of in personD. Biased because responses may be inaccurateE. Biased because volunteer samples are almost always biased
From lab 1.1:■A picture of all the sample averages calculated for the average word length of the Gettysburg address:Most missed Question:Did we use simple random sampling?NoActual average word length: _4.3____Did we have biased samples? How so?How could we get a true random sample?
Reminders:Look for an email from with a link to schedule your exam 1 time (or go to testing.psu.edu)Do not pick a time that overlaps with lecture or lab – any other time you want is fineYour options will be all day for two days – pick one day and one time slot that is best for youThere will be extra GSG for exam review. Check Canvas.Exam 1 is on chapter 1 only. We will have lecture and lab on the exam days and we will be moving on to new material. We will not review for the exam while the exam is in progress
STATISTICS 200: EXPERIMENTS AND OBSERVATIONAL STUDIESSection 1.3
Collecting Sample DataData Format and Variable typesPopulations, samples,biasExperiments andObservational Studies,Association versusCausationElements of ExperimentsBlindingPlacebosConfounding variablesMatching
Association:■Recall: we are often interested in the relationship between two variables.Two variables are associated if values of one variable tend to be related to values of the otherTwo variables are causally associated changing the value of one variable influences the value of the other variable.Causation: