Experimental methods to control variance should guide us in how to select ways to mitigate threats to validity.

We're skipping up over the time-based designs in Babbie, but having a basic understanding of what's involved in time series is helpful. Want to see whether some change has an effect. To do that, you need two points in time. But interviews that are retrospective do not offer time comparisons.snapshots of social media are one wayhigher education: entering college freshmen in their first year, every year-->it's a cohort designthere are other types, each with its own tradeoffs

the drivers/speeding-->regression to the mean

in both cases they've gone back to archival records and showed how you can get two points in time

but whenever you deal with archival records, you have to account for how the recordkeeping can create artifacts (things that shouldn't be there) [shift changes, ambient things]

key vocabulary
independent variable: the stimulus, which you manipulate to determine effect
dependent variables: effect

T1 measure the dependent variables for baseline [pre test]

T2 introduce the stimulus

T3 measure the dependent variables again [post test]

the difficulty lies in selecting the samples so they match in both conditions

"all about isolating variance" -- always trying to do this, but most explicit in experiments

divide people into categories that are as discrete as possible

the more continuous, fuzzy, variables are the dependent variables

experience in this one is also an IV?

path model: survivors --> represent experience --> artifacts

the represent experience variable is an intervening variable; we need to know how the people define their experience

MT: census, school records, etc. would be one way to follow the movement of the population and compare with the sample to see how representative it is

 

Rob: how do you differentiate multiple pre and post tests from a time series experiment?

When you can't assign people to the different groups in each condition, it becomes a quasi-experiment-->Campbell

 

 

p. 241 shows two cases of your variable

the more heterogeneous (wider the variance within) each group, the more subjects you need

list in Babbie on 238

the longer the study, the more ppl you need in the study bc attrition over time

the "all's well" literature bias-->don't assume tktk

"hot stuff" bias

anticipate the criticisms, explain each choice I make, and acknowledge what I can't control

more important to be able to explain your choices, how much strength how much claim you can make internal and external validity

Mario's paper

How do survivors represent their experience in material artifacts?

gets at some sense of meaning that transcends the particular case; could be asked in multiple environments

then operationalize survivors, experience, representation, material artifacts

survivors: living in ES?; living there bt x and y dates?; descendants?

represent: what was chosen to keep and preserve

material artifacts: photos, papers, newspapers, records, audio, video, household objects

IV: could do by age, generation, gender, political role,

IV: survivors

person in ES 1979-1992

= 50%

<= 50%

first-generation descendants

second-generation descendants

could look at experience in a few ways: things associated with the deeply personal, and the things that are a more public representation

could do a pilot test study on the diaspora with ppl here in LA

Natascha's project

Does Twitter use affect student engagement in a German language classroom?

conditions: use T; not use T

how operationalize engagement?

finding something that is comparable for a control group is difficult; you need to have two forms of social interaction (say, public versus private)

neutral grading

tasks have to be as close as possible

effect has to be tk

measure of student engagement

is there another method that will help her get to the thing she wants to see?

if you want to look at the effect of a technology, you have to use this experiment method-->set a minimum and measure which ones do it more

minimum threshold and rate of posting

but then you have a problem with the base rate of social media interaction

MT: does Twitter make ppl focus on the key things more, since it is limited in length?

MT: ranking favorites?

bc the question is causal, you have to use experiment to isolate

Dustin's article analysis-->the researcher uses available data, which is a limitation; the significance of the finding is hard to discern

Borgman: can you get a control group with and without television? this is a snapshot in time;

there was a notable change in media consumption

the risk is that the groups are moving together-->historical threat to validity

since you only look at this slice (big data/little data problem), you don't see the effect; too narrow

what might you have done if you could go back? bc it's Public Opinion Quarterly, the audience is the one that does big public opinion polls; they know sampling and matching inside out and backwards (only need to show that they've done what's expected; the Schram literature was a landmark in the field; people reading this would know that material intimately; the cleverness of this piece is finding a way to get a control group with and without television (if you could find someone who hadn't watched tv: Nell); this is a shot in time when you could make that comparison; the rollout of tv created records that a lot of others could then use; surprising that there's not more discussion. the results is often fairly short, but the discussion is the meaning explanation; this was an early quasi-experimental piece; it's a rigorous design and it's a snapshot in time that lets us see how hard it is to get control groups on things; as the internet became a household item, ppl went back to the tv studies and tried to replicate; the landmark of how a new medium changed social engagement

a whole lot of research came out of this: "tv doesn't tell you what to think but it tells you what to talk about"

MT: how does that compare to what we think about social media?

this makes a set of assumptions: we assume that media use is a zero-sum game; pairwise comparison, but notice it's only comparing two (not newspaper and radio)

then moved into time-shifting media use; asynchronous media

series of shifts