The same test for every design

What this lesson teaches: To compare two designs, give both the same test; then the only difference is the design.

Video rendering. This video is in the Peps pipeline (about 60 seconds, 121 spoken words). Until it lands, the storyboard below is the video, beat by beat.

The script (narration and what is on screen) — open

#	Narration	On screen
1	In Mr. Park's class, Erin and Luis have each built a pencil holder. They want to know whose holder stays up better when the desk is bumped.	Mr. Park's classroom; Erin's tall holder and Luis's wide holder, each on its own desk, side by side; chips IVY and LUIS; no title slide
2	Erin bumps her desk gently. Her holder stays up.	Erin's desk wobbles with one short motion line; chip GENTLE BUMP; her holder stays up
3	Luis bumps his desk hard. His holder tips over.	Luis's desk wobbles with three long motion lines; chip HARD BUMP; his holder tips and the pencils spill
4	So is Erin's holder better? Nobody can tell. The bumps were different. This is not a fair test.	a question mark between the desks; chip NOT A FAIR TEST
5	Now they bump both desks the same way, hard. Erin's holder tips over. Luis's holder stays up.	both holders upright again; both desks wobble with three long motion lines; chip HARD BUMP over each; Erin's tips, Luis's stays
6	The bumps were the same, so the holders made the difference. This is a fair test.	chip FAIR TEST
7	So, here's what we've seen. To compare two designs, give both the same test. Then the only difference is the design.	rule slide reuses the two desks with HARD BUMP over each; rule text
8	Okay, now your turn.	the attached question appears

In Mr. Park's class, Erin and Luis have each built a pencil holder. They want to know whose holder stays up better when the desk is bumped.

Different bumps

Erin bumps her desk gently. Her holder stays up.

Luis bumps his desk hard. His holder tips over.

So is Erin's holder better? Nobody can tell. The bumps were different. This is not a fair test.

The same bump

Now they bump both desks the same way, hard. Erin's holder tips over. Luis's holder stays up.

The bumps were the same, so the holders made the difference. This is a fair test.

	Erin's desk	Luis's desk	Fair?
First try	gentle bump	hard bump	No. The bumps were different.
Second try	hard bump	hard bump	Yes. The bumps were the same.

To compare two designs, give both the same test.

Then the only difference is the design.

Okay, now your turn

One easy question straight after the video: the student answers it to move on.

After the video

Kyle compares two paper cups to see which holds water longer. Which is a fair test?

Quiz

(a) fluency: two designs and a pair of tests; fair? yes / no. Fresh contexts, never the lesson's own pencil holder.

Question 1

Kyle throws plane A gently and plane B hard. Is this a fair test?

Question 2

Kyle throws plane A and plane B the same way from the same line. Is this a fair test?

Question 3

Kyle puts ten coins on bridge A and ten coins on bridge B. Is this a fair test?

Question 4

Kyle puts ten coins on bridge A, and ten coins and a stapler on bridge B. Is this a fair test?

Question 5

Kyle flies kite A on a windy day and kite B on a day with no wind. Is this a fair test?

Question 6

Kyle flies kite A and kite B on the same field at the same time. Is this a fair test?

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