Whether you’re conducting research, reading about research, or finding out research methods so you can ace your research techniques course, you should know precisely what a confounding change is. If girlfriend think you’ve obtained it, climate this no the article for you. Yet if she confounded through the idea the a confound, climate this write-up may aid you to watch the light.A somewhat formal definition of a confounding change is “an extraneous variable in an experimental style that correlates v both the dependent and independent variables”. This is a disastrous definition, full of words and also phrases that median nothing to 99% that the population. So, let’s begin with a standard concrete example.

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AN OLD CLASSIC: MURDER and ICE CREAM

It is known that transparent the year, killing rates and also ice cream sales are highly positively correlated. That is, as murder prices rise, so does the revenue of ice cream. There room three possible explanations because that this correlation:

Possibility #1: Murders cause people to acquisition ice cream. One can imagine a civilization where this is true. Perhaps once one is murdered, they are resurrected together zombies who generally feed on ice cream cream.

Possibility #2: Purchasing ice cream reasons people to murder or get murdered. Again, one might imagine a civilization where this is true. Perhaps when one eats ice cream, those without ice cream cream become jealous and murder those v ice cream.

Possibility #3: over there is a third variable—a confounding variable—which reasons the boost in BOTH ice cream cream sales and also murder rates. Because that instance, the weather. Once it’s cold and also Wintery, human being stay at house rather 보다 go outside and murder people. They likewise probably don’t eat a lot of ice cream. When it’s hot and Summery, people spend an ext time outside interacting with every other, and also hence are an ext likely to acquire into the type of cases that cause murder. They are additionally probably buying ice cream cream, due to the fact that nothing to win the sound the an ice cream van on a blazing Summer day.

In this example, the weather is a variable the confounds the relationship between ice cream sales and also murder rates. Friend may also recognize this as the so-called third change problem, which describes the truth that any type of time us observe a relationship among two variables, there’s constantly the possibility that some 3rd variable which us don’t know about is responsible because that (“confounding”) the relationship.

A CONCRETE instance WITH A pretty PICTURE

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If friend still don’t obtain it, i have got one more example and also a pretty snapshot to go with it. Imagine you’d prefer to study the relationship between the pressure you apply to a ball and the distance the round travels. Naturally, you predict the the an ext force girlfriend apply, the further the round will travel. You produce an experiment through two conditions. Currently you need to be eyeballing that pretty picture I told girlfriend about. In condition 1, you apply a 10 lb pressure to the ball and also measure the street traveled. In problem 2, you apply a 5 lb force to the ball and also measure the distance traveled. After you run your experiment, girlfriend observe the the round travels more in problem 2 보다 it walk in problem 1. In various other words, you find that the less pressure you apply, the additional the sphere travels. Need to you conclude that Isaac Newton to be wrong? No. As must be pretty clear from the pretty picture, there’s a clear confounding change in this experimental design: the edge of the slope. Offered the presence of this confound, we have actually no method of understanding which change – pressure or edge – is responsible because that the readjust in the street the sphere travels.

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This illustrates why it’s so vital to constantly be top top the lookout because that confounds. Confounds have the right to make united state reach conclusions that are wrong; confounds have the right to make united state look stupid. Or, to usage slightly an ext technical language: confounding variable = BAD.