Causation and Experimental Design (4.1)

Causal relationship

5 criteria should be considered when trying to establish a ____ ____ 1. empirical association -Shows there's association 2. temporal priority of the independent variable -Shows there's a temporal ordering (a causes b) 3. nonspuriousness -Rule out rival causal factors 4. identifying a causal mechanism 5. specifying context in which effect occurs -Context is setting First three of the criteria are considered as requirements for identifying a causal effect -You must establish these 3 to claim a causal relationship Evidence that meets the other two criteria— (4) identifying a causal mechanism and (5) specifying the context in which the effect occurs—can considerably strengthen causal explanations -Research designs that allow us to establish these criteria require careful planning, implementation, and analysis -Many times, researchers have to leave 1 or more of the criteria unmet and therefore are left with some important doubts about the validity of their causal conclusions; or they may avoid even making any causal assertions

Causal mechanism

Criteria A ____ ____ is the process that creates the connection between variation in an IV and the variation in the DV it is hypothesized to cause Many social scientists (and scientists in other fields) argue that no ____ ____ is adequate until a mechanism is identified Education and income example: -Graduate from college in 2006----> Get new job with degree and make more money in 2007 -The ____ ____ is that the education provided the qualifications and training that allowed you to get a higher paying job In other words, the story about how X affected Y has to make logical sense

Context

Criteria No cause has its effect apart from some larger ____ involving other variables When, for whom, and in what conditions does this effect occur? A cause is really one among a set of interrelated factors required for the effect Unfortunately for social scientists, social phenomena do not occur in a vacuum. We must consider all factors that are affecting an outcome Education and income example: -Graduate from college in 2006----> (good economy, profession in demand, etc.) Get new job with degree and make more money in 2007 -Not the case in bad economy, profession not in demand, etc. -There are a number of other factors that will affect your ability to get a good paying job after graduation: the economy, the type of profession you entered, your previous experience, etc.

Empirical association

Criteria The first criterion for establishing a causal effect is an ____ (or observed) ____ (sometimes called a "correlation") between the IV and DV IV and DV must vary together -When one goes up, the other goes up (or down) at the same time -Change in X is associated with change in Y ΔX ----> ΔY -Arrow= associated with -Triangle= change The longer you stay in school, the more money you will make later in life -A change in an IV correlates, or is associated with, change in a DV -If there's no association, there can't be a causal relationship

Nonspuriousness

Criteria "Spurious" means false or not genuine Relationship between two variables is spurious when it is due to variation in a third variable; so what appears to be a direct connection is not -Spurious value is related to X and Y Researchers must be able to rule out rival causal factors Have you heard the old adage "Correlation does not prove causation"? It is meant to remind us that an association between two variables might be caused by something else -In regions where there are more storks, there are also more babies born per family -However, the real causal variable is whether or not a region is rural or urban. Rural farm families have more children than urban families (they need the help!), and rural areas have more storks The fire engines and dollar amount of damage from a fire and the ice cream sales and drownings examples are the other two

Temporal priority of IV

Criteria The change in X must occur before the change in Y -This is the criterion of time order, or the ____ ____ __ ____. ΔX----> ΔY t1 t2 Graduate from college in 2006----> Get new job with degree and make more money in 2007

Causes

Identifying ____—figuring out why things happen—is the goal of most social science research Unfortunately, valid explanations of the ____ of social phenomena do not come easily

True experiments

____ ____ have at least 3features that help us meet these criteria 1. Two comparison groups (in the simplest case, an experimental group and a control group), to establish association 2. Variation in IV before assessment of change in the DV, to establish time order 3. Random assignment to the two (or more) comparison groups, to establish non-spuriousness Experimental research provides the most powerful design for testing causal hypotheses because it allows us to confidently establish the first 3 criteria for causality—association, time order, and non-spuriousness We can determine whether an association exists between IV and DV in a ____ ____ because there are 2 or more groups that differ in terms of their value on the IV -One group receives some "treatment" that is a manipulation of the value of the IV -This group is termed the "experimental group" -In a simple experiment, there may be one other group that does not receive the treatment; the "control group"