Rocket is at the Windowsill with the ruler at exactly the same time as yesterday. "Day one," he says. "Station: six point five. Control: six point eight."
Raven writes it down. "What do you notice? Do not decide yet. One day is one point."
"The control is still taller," Rocket says, disappointed. "But look at the stems. The station sprout is standing straighter."
Nova hovers over the two jars. "You have three criteria," she says. "Score them one at a time."
Rocket makes three columns. "Height: control ahead. Color: both green. Upright: station ahead."
"Now you are judging like an engineer," Raven says. "A design can win one test and lose another."
The Next Generation Science Standards page on engineering design describes how engineers judge and improve a solution.
This table gathers four of its statements. Read each one and ask how it applies to your station.
| Engineering idea | What it means for your station |
|---|---|
| The more precisely criteria and constraints are defined, the more likely the solution will succeed | Your three criteria and four constraints are the yardstick |
| There are systematic processes for evaluating solutions against the criteria and constraints | Score each criterion for both jars, every day, the same way |
| A solution needs to be tested, then modified on the basis of the results, to improve it | Friday's redesign uses what the data shows |
| One design may not perform best in every test; the best characteristics of each can be combined | Keep the part that worked, change the part that did not |
Use your table from Wednesday. For each criterion, write which jar is ahead today, or write tie.
Height gained: subtract day 0 from today for each jar. The bigger gain is ahead.
Leaf color: compare the words you wrote. Green beats pale green, and pale green beats yellow.
Upright stems: compare upright, leaning a little and leaning a lot.
Then check constraints: still fits the space, still only home materials, still only window light.
Two days of data is not enough to decide. It is enough to notice a trend and plan a change.
| Criterion | Station so far | Control so far | Which is ahead? |
|---|---|---|---|
| Height gained (cm) | |||
| Leaf color | |||
| Upright stems | |||
| All constraints met? |
| Statement | True or false? |
|---|---|
| A design can win on one criterion and lose on another. | ? |
| Two days of data is enough to be certain which jar wins. | ? |
| Constraints are checked during the test as well as at the start. | ? |
| The best characteristics of different designs can be combined. | ? |
Careful judging. Tomorrow you redesign using the data and begin the Cells and Systems report.