Tuesday

On Saturday, the crew sits by the Commons door with a clipboard. Their job is a door count: how many people come in.

Comet has a plan. "Let's write a number every single minute! Then we will know everything."

Wren does the math in the margin. "Ten hours is six hundred minutes. That is six hundred numbers on one sheet."

"Too many?" Comet asks.

"Maybe," Wren says. "Once an hour is only ten numbers. What do you notice about what each one tells us?"

Nova hovers above the clipboard. "Would you like a hint?" she asks. "Every choice keeps some detail and drops some. Decide what the council needs."

Comet taps her pencil. "So how often should we count?"

Ways of collecting data can differ in the storage they need, the detail they collect and how often they sample.

Some data, like daylight through a window, change smoothly over time. These are called analog data.

Analog data can be closely matched digitally by measuring them at regular intervals. Each measurement is called a sample.

Using samples to stand in for something that changes smoothly is an example of abstraction.

The crew's door count uses the same idea. They choose a regular interval and write one number for each one.

Here is the crew's hourly count. Each number is how many people came through the door in the hour that starts at that time.

This is made-up data from the Commons Count story.

For one hour, Wren also counted every 15 minutes. Here is the 4 pm hour, split into four parts.

The four parts add up to 14, the same as the hourly count. But now the crew can see more people arriving near 5 pm.

More detail meant four numbers instead of one. A whole day at this rate needs four times as many numbers.

Sharp thinking. Tomorrow in Count Lab you will turn a stack of answers into a tally and a frequency table.