### What is the right periodicity?

It seems that intensive measurement is on the rise. There are a number of different kinds of things that are difficult to recall sufficiently over longer periods of time where it might be preferred to ask the question more frequently with a shorter reference period. For example, the number of alcoholic drinks consumed by day. More accurate measurements might be achieved if the questions was asked daily about the previous 24 hour period.

But what is the right period of time? And how do you determine that? This might be an interesting question. The studies I've seen tend to guess at what the correct periodicity is. I think it's probably the case that it would require some experimentation to determine that, including experimentation in the lab.

There are a couple of interesting wrinkles to this problem.

1. How do you set the periodicity when you measure several things that might have different periodicity? Ask the questions at the most frequent periodicity?

2. How does nonresponse/attrition fit into this? If some people will only respond at a certain rate, what should you do? Is it better to force the issue with them, i.e. make an ultimatum that they participate at the rate we desire or not at all; or better to allow them to participate at their preferred rate?

I'm sure the answers vary across the substantive areas of interest. But it does seem like an interesting set of problems in the evolving world of survey research.

### The Cost of a Call Attempt

We recently did an experiment with incentives on a face-to-face survey. As one aspect of the evaluation of the experiment, we looked at the costs associated with each treatment (i.e. different incentive amounts).

The costs are a bit complicated to parse out. The incentive amount is easy, but the interviewer time is hard. Interviewers record their time for at the day level, not at the housing unit level. So it's difficult to determine how much a call attempt costs.

Even if we had accurate data on the time spent making the call attempt, there would still be all the travel time from the interviewer's home to the area segment. If I could accurately calculate that, how would I spread it across the cost of call attempts? This might not matter if all I'm interested in is calculating the marginal cost of adding an attempt to a visit to an area segment. But if I want to evaluate a treatment -- like the incentive experiment -- I need to account for all the interviewer costs, as best…

### Goodhart's Law

I enjoy listening to the data skeptic podcast. It's a data science view of statistics, machine learning, etc. They recently discussed Goodhart's Law on the podcast. Goodhart's was an economist. The law that bears his name says that "when a measure becomes a target, then it ceases to be a good measure." People try and find a way to "game" the situation. They maximize the indicator but produce poor quality on other dimensions as a consequence. The classic example is a rat reduction program implemented by a government. They want to motivate the population to destroy rats, so they offer a fee for each rat that is killed. Rather than turn in the rat's body, they just ask for the tail. As a result, some persons decide to breed rats and cut off their tails. The end result... more rats.

I have some mixed feelings about this issue. There are many optimization procedures that require some single measure which can be either maximized or minimized. I think thes…