Chapter 4: Measurement and Units of Analysis
First, suppose a researcher has decided to measure alcoholism by asking people to respond to the following question: Have you ever had a problem with alcohol? If we measure alcoholism in this way, it seems likely that anyone who identifies as an alcoholic would respond with a yes to the question. So this must be a good way to identify our group of interest, right? Well, maybe. Think about how you or others you know would respond to this question. Would responses differ after a wild night out from what they would have been the day before? Might a teetotaler’s current headache from the single glass of wine he had last night influence how he answers the question this morning? How would that same person respond to the question before consuming the wine? In each of these cases, if the same person would respond differently to the same question at different points, it is possible that our measure of alcoholism has a reliability problem. Reliability in measurement is about consistency. If a measure is reliable, it means that if the same measure is applied consistently to the same person, the result will be the same each time.
One common problem of reliability with social scientific measures is memory. If we ask research participants to recall some aspect of their own past behaviour, we should try to make the recollection process as simple and straightforward for them as possible. Sticking with the topic of alcohol intake, if we ask respondents how much wine, beer, and liquor they have consumed each day over the course of the past three months, how likely are we to get accurate responses? Unless a person keeps a journal documenting their intake, there will very likely be some inaccuracies in their responses. If, on the other hand, we ask a person how many drinks of any kind he or she has consumed in the past week, we might get a more accurate set of responses. Reliability can be an issue even when we are reliant upon individuals to accurately report their behaviours.
We can look at another example. Perhaps a field researcher is interested in observing how alcohol intake influences interactions in public locations. She may decide to conduct observations at a local pub, noting how many drinks patrons consume and how their behaviour changes as their intake changes. But what if the researcher needs to use the restroom and misses the three shots of tequila that the person next to her downs during the brief period she is away? The reliability of this researcher’s measure of alcohol intake, counting numbers of drinks she observes patrons consume, depends upon her ability to actually observe every instance of patrons consuming drinks. If she is unlikely to be able to observe every such instance, then perhaps her mechanism for measuring this concept is not reliable.