Data Dive 2.3

Do rats take the weekend off?

Some patterns have a reason. Some are just luck. How can you tell?

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?

A student notices that New York gets fewer calls about rats on Saturday.

She says rats must be less active on weekends.

Write it down before you lookDo you think rats take weekends off? Write yes or no, and what else might explain it.
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Step 2 of 5 · Look

Rat calls by day of the week

Rat complaints by day of the weekNew York, 2024complaints filedday of the weekcomplaints filed3,4166,83206,832Mon6,427Tue6,148Wed6,130Thu5,736Fri4,019Sat4,434Sun

New York, all of 2024. One bar is one day of the week.

How to read it. Each bar is one day of the week. Its length is how many rat calls New York got on that day, added up across all of 2024.

Find out
  1. Read the bars from Monday to Saturday. What do you notice?
  2. Who changes on Saturday: the rats, or the people calling?
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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=weekday_nyc_rat_complaints.csv&mark=bar

  1. Under across, pick weekday. Under up, pick complaints_2024. Set order to file, so the days stay in order. Describe the shape in one word.
  2. Press shuffle three times. It deals the numbers to random days. Does the smooth slope ever show up by luck?
  3. Open weekday_socal_quakes.csv the same way. It counts earthquakes by day of the week. Describe its shape in one word.
  4. Shuffle the earthquakes three times. Do the shuffled charts look any different from the real one?
  5. Which pattern would you bet shows up again next year? Why?
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Step 4 of 5 · Say it

Your answer, in one sentence

I think the drop in rat calls is <real or luck> 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 drop in rat calls is real, because calls fall a little every day from Monday to Saturday, in order. I checked by shuffling the days, and the smooth slope never came back. The earthquake chart looked the same shuffled or not.
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Step 5 of 5 · What you found

Check your numbers

Mon 6,832; Sat 4,019
the most and the fewest rat calls
1.70x
Monday's rat calls compared with Saturday's
Wed 995; Sun 753
the most and the fewest earthquakes, in no order
The big idea: a pattern with a reasonA real pattern usually has a reason you can name. On weekdays, people are at work near a phone. Earthquakes do not know what day it is, so their ups and downs are luck. Shuffling is a quick test: luck looks the same shuffled, and a real pattern breaks.
One more thing to think aboutRat calls go back up on Sunday. What do people do on Sunday that they do not do on Saturday?
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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.

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

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