Fixed and Relative Time

Some Variables might be defined just at one particular point in time, such as the number of people attending the Olympics 2016 closing ceremony on July 1 or the performance of a student at a particular exam. Fixed time can be specified, usually with some kind of date, like this:

Number of people attending Olympics 2016 closing ceremony,  Time=July 1

… otherwise we assume the time is “relative” rather than fixed.

Sometimes we have general time Rules which are valid for quite a range of time but do not apply to any particular time; nevertheless a delay is implied or can be specified like this:

Student exam performance

(A bit later)Revision behaviour

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As this vague delay of “a bit later” is the default, it can usually be left off.

This general time Rule can be applied in particular to fixed time-points:

Student exam performance, Time=exam in early summer 2018

Performance-boosting workshop, Time=February 2018

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We usually assume that the delay is implied to fit the gap between the time points, but we can specify it too:

Student exam performance, Time=exam in early summer 2018

(3-4 months later)Performance-boosting workshop, Time=February 2018

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When several Variables share a fixed time-point (e.g. baseline, or year_1), it can be very convenient to group them with grouping boxes.

-Endline

Student achievement (endline)

-Baseline

Student achievement (baseline)

Student ability

Teacher skills

Our Theories about specific projects and programmes are usually situated in some fixed time - today, next month, next year etc. Whereas the kind of more universal social science Theories we (hopefully) draw on to get evidence for our Theories are usually situated in relative time.

In this chapter we look at some more details about how Variables can be positioned in time, relatively or absolutely.

Some Variables might be defined just at one particular point in time:

Number of people attending Olympics 2016 closing ceremony on July 1

… in which case they can and perhaps should be marked as such. Features can be useful for specifying time points:

Number of people attending Olympics 2016 closing ceremony, Time=July 1 2016

Delays

For any causal Rule, the Consequence has to happen at least a little bit later than the Influence. Ideally we should say how long the likely delay is.22

A general time Rule

Windows are broken

(A bit later)Large explosion in vicinity

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1. In some cases there is probably a more complicated continuous relationship even involving differentials etc; we won’t deal with those in any depth here.