How a clerk reads a dwell chart without a statistics course

A dwell chart answers one question: how long did readers stay with a named section, in a named window of days. It does not answer whether they were happy, whether the hall should hire, or whether the portal is “modern.” When a clerk has to read a plate aloud, the order matters more than the drawing.

Start with the title. If it does not name the section and the dates, send the plate back. Then read the unit. Minutes are not visits. A three-minute dwell on a notice that is three sentences long is a different story from a three-minute dwell on a form with twelve fields.

Next, look at the caution line. We print one when the sample is thin — a village kiosk that saw forty uses in ten days, an evening hour with a frozen search box. A chair who skips the caution will invent a city-wide law from a corridor.

Only then compare bars. Compare the same section to itself across hours, not a library catalogue to a tax form. If the committee wants a ranking of departments, refuse; rankings of people have no place on a Layergrid plate.

When you speak, say what moved. “After six, dwell on search falls to almost nothing, at the same minute the terminal seizes.” That sentence can go downstairs. “Engagement is low” cannot.

We still meet clerks who apologise for not having studied charts. They do not need a course. They need a plate whose type survives a photocopier and a commentary that uses the names of rooms they already keep.