Data Dive 2.1

Which part of New York has the most rats?

The city has numbers. The question is what they count.

You will need paper and a pencil, and a browser for step 3

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Step 1 of 5 · Your guess

What do you think?

Two students argue about which part of New York City has the most rats. The city has five boroughs: Brooklyn, Manhattan, Queens, the Bronx, and Staten Island.

One student pulls up the city's 311 numbers and says that settles it.

Write it down before you lookDo the city's numbers settle it? Write yes or no, and one reason.

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Step 2 of 5 · Look

Rats in New York, by borough

New York City 311, 2024. One bar is one borough.

How to read it. Each bar is one borough. The longer the bar, the more times people there called 311 to report a rat in 2024.

Find out

Which borough is on top? Which is at the bottom?
Read the line above again. Does one bar count rats, or calls?

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Step 3 of 5 · Try it

Now you try it, on the same data

This opens the pool, the site's chart tool. The words in bold below are buttons and menus you will see on the screen.

Do these five things

Open the pool on this file: data.sfhsbta.com/thepool?file=choropleth_nyc_rat_complaints_by_borough.csv&mark=bar

Under across, pick borough. Under up, pick complaints_2024. Set order to by value. Which borough is first?
Hover the top bar and the bottom bar. Divide the top number by the bottom one.
In one sentence, write what one bar counts. Hint: it is not rats.
Type a caption under the chart that says exactly what was counted, so nobody could read it as a count of rats.
Think of a reason a borough could have lots of rats but few calls. Write it down.

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Step 4 of 5 · Say it

Your answer, in one sentence

I think the city's numbers <do or do not settle it> because <what the chart shows> and I checked it by <what you did to the chart>.

The last part matters most. It shows you did not just look at the chart, you tested it.

Here is one exampleI think the city's numbers do not settle it, because each bar counts phone calls about rats, not rats. I checked by writing the caption ‘calls to 311 about rats’ and the argument stopped making sense.

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Step 5 of 5 · What you found

Check your numbers

Brooklyn: 15,099

the most calls about rats

12x

Brooklyn compared with Staten Island

a call

what one bar counts

The big idea: counting reports, not the thingLots of data counts reports about something, not the thing itself. This chart shows where people call about rats. That is not the same as where the rats are. Always ask: what exactly was counted?

One more thing to think aboutEarthquake records in Southern California jump in the 1930s. The ground did not change. That is when better earthquake sensors were put in. Can you think of another number that went up because people started counting better?

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After the dive

The charts you used today

the bar

Bar length is the value, so it only means anything measured from zero. Start the axis anywhere else and the lengths stop matching the numbers.

What it leaves outOrder is a choice. Sorted by size it is a ranking; sorted by name it is a lookup; and the same bars say different things in each.

the line

A line follows one thing over time. Read it left to right and watch which way it leans — that lean is the whole story. A dashed stretch is a guess, not something anyone measured.

What it leaves outThe line implies every point between the dots, and nobody measured those. Where you start and stop it decides what the trend looks like.

library · ladder · dives · the pool · this dive’s worksheet

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