2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

Disadvantage: Will not work will all populations. You need to make sure the clusters reflect the variation that is present in the population. For example, what if one of the homerooms was for only gifted and talented students. Would that be representative of all the population?

1 in k Systematic Sampling This is a procedure that can be used when the population can be sequentially organized. To use it, first choose a starting point at random from the first k individuals. Then choose every kth individual after that. "k" is often selected so that a certain sample size is produced. If N= population, and n = sample size, then k = N ÷ n.

Advantage: it is convenient when you already have a list of the units in your population.

Disadvantage: It can lead to bias. For example, if you are choosing every 20 th item in a list of invoices, you may keep selecting many of the same customers.

It’s possible to do a repeated systematic sampling . This technique avoids bias due to periodicity. In this case, you take several smaller systematic samples with a different random starting point (rather than using a single pass-through of the whole). Source of bias: measurement or response bias Besides selection bias, another type of bias is called measurement or response bias. This occurs when the method of observation tends to produce values that systematically differ from the true value in some way.

1) For example, an improperly calibrated scale is used to weigh items, or

2) Tendency of people not to be completely honest when asked about illegal behavior, unpopular beliefs, or something they find embarrassing (for example, suppose we want to survey high school students on drug abuse and we used uniformed police officers to interview students - I doubt we would get honest answers!)

3) Even the appearance or behavior of the person asking the questions can result in response bias.

4) And this one is my favorite - questions on the survey are worded in such a way that it tends to influence the response. That's one reason, an Institutional Review Board (IRB) will ask for your survey questions as part of your Human Subjects Submission.

Example of a poorly written question :

It is estimated that disposable diapers account for less than 2% of the trash in today's landfills. In contrast, beverage containers, third-class mail and yard waste are estimated to account for about 21% of trash in landfills. Given this, in your opinion, would it be fair to tax or ban disposable diapers? Gallup Survey. (1994, May 17). American Paper Institute. Wall Street Journal .

Source of bias: non-response This occurs when responses are not obtained from all individuals selected for inclusion in the sample.

Example: The phone rings - you answer. The person says "Hello, do you have time for a survey about ..." and you hang up!

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