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Good evidence is chosen for the question: about it, checkable, and measuring both sides of a comparison the same way.
Paper packet. Every task here also exists on screen, where it is checked automatically; answers written on paper are not assessed by Nydus. When you are back at a device, enter your answers there.
You will choose the check that would settle a simple question — one that is about the question, can be done, and measures both sides of a comparison the same way — and spot a check that looks at one side only or changes two things at once.
You can judge the reasons other people give. Now you go first: before anyone argues, ask what could be looked at, counted or measured that would settle the question.
| Term | What it means |
|---|---|
| This lesson's terms | Evidence is something that can be looked at, counted or measured. A check settles a question when its result would answer that question. A fair comparison measures both things the same way, so any difference comes from the thing being compared. |
| Supported conclusion | The conclusion the stated reasons reach, including the limits on its group, time or conditions. |
Question: do the tomatoes by the wall grow bigger than the ones by the gate? Here are four things someone could find out:
Only the third settles it. Three questions pick it out:
That last point catches careful people too. More and better and quicker are comparisons, and a comparison needs both sides, measured the same way: the same day, the same scales, the same kind of plant. If you change two things at once — different spots and different watering — you cannot tell which one made the difference.
And when the result comes in, say what it shows and no more: one garden, one summer.
Another way: picture
A see-saw test: to find which child is heavier, both sit on the same see-saw at the same distance from the middle. Weigh one child and not the other, and the see-saw tells you nothing.
Another way: steps
Useful evidence bears on the question and could lead you toward either answer. If you ask whether a bag is waterproof, checking only whether it looks shiny will not settle the issue. You need a suitable test of whether water gets inside under the conditions being claimed. First say what result would support the claim and what result would count against it.
For a comparison, keep other important conditions alike. If you compare two paper towels, use equal amounts of water, equal-sized pieces and the same measuring method. Otherwise a difference might come from the setup rather than the towel. You do not have to know every scientific term to ask whether the comparison gave both options a fair chance.
Record results before choosing the conclusion. A table with a row for each trial helps you notice a result you might otherwise forget. Repeating a check can reveal an unusual first result or a mistake in measuring. Repetition alone does not fix an unfair setup, so examine the method as well as the number of trials.
Some questions need records rather than experiments. A club's opening time is best checked against its current notice or a responsible organizer. A person's preference is best checked by asking that person. You should not run an experiment on somebody to answer a question that their own report can answer. Match the kind of evidence to the kind of claim, and state what your chosen check leaves unanswered.
Question: Is the canal path a quicker way to the station than the main road? Which check would settle it?
The supported answer is: Time the walk both ways, on the same kind of day, several times each.
The distinction in this case is that quicker than needs both routes timed, and more than once.
Question: Did the new posters get more people to the book swap? Which check would settle it?
The supported answer is: Compare the number of people at the book swaps before the posters with the number after.
The distinction in this case is that more means more than before, so both the before count and the after count are needed.
Question: Which ball bounces higher, the red one or the blue one? Which check would settle it?
The supported answer is: Drop both balls from the same height onto the same floor, five times each, and measure every bounce.
The distinction in this case is that a fair comparison drops both balls the same way and measures both.
Question: Does Pip's dog eat more on cold days than on warm ones? Which check would settle it?
The supported answer is: Weigh the food the dog eats every day for a month and note each day's temperature.
The distinction in this case is that the question compares cold days with warm ones, so it needs many days of both.
Question: Do sunflowers grow taller in the sunny bed or the shady bed? Which check would settle it?
The supported answer is: Plant the same seeds in both beds, water them the same, and measure every plant in both beds after six weeks.
The distinction in this case is that the question compares two beds, so both must be measured, grown the same way.
Match each question to the check that would settle it.
Is the pond deeper than a meter in the middle? / Do more people use the park on Saturday or on Sunday? / Does the new lamp light the path all the way to the gate? / Did the fridge stay cold while we were away? / Lower a marked pole into the middle of the pond. / Count the people at the gate all day on both days. / Walk the path after dark with the lamp on. / Read the fridge thermometer's record of the week.
Is the pond deeper than a meter in the middle? is settled by measuring the depth there. Do more people use the park on Saturday or Sunday? needs counts on both days. Does the new lamp light the path all the way to the gate? is settled by looking at night; did the fridge stay cold while we were away? by the fridge thermometer's record.
Put the five steps of a fair check in order.
Write the exact question. / Decide what to count or measure. / Measure both sides the same way. / Compare the results. / Say what the result shows, and no more.
Write the exact question first, then decide what to count or measure. Measure both sides the same way, then compare the results. Last, say what the result shows — and no more than it shows.
Ivy plans a test of which ball bounces higher, the red one or the blue one. Mark the step that makes her test unfair.
Drop both balls onto the same patch of floor. / Drop the red ball from two meters and the blue ball from one meter. / Measure every bounce with the same ruler. / Drop each ball five times.
A fair test changes only the ball, so everything else must be the same for both. Dropping the red ball from two meters and the blue one from one meter changes the height too, so a higher red bounce could come from the height and not the ball. The same floor, the same ruler and five drops each are all fair.
A news story: the city council put speed bumps on Station Road in March. Did they slow the traffic down? Which evidence would settle the question?
The supported answer is: Speed-camera readings at the same spot for a month before the bumps and a month after.
The question compares speeds on Station Road before and after the bumps. Speed-camera readings from the same spot for a month before March and a month after measure exactly that. Complaints are about feelings, one car on one day is one case, and other towns are other roads.
Sometimes a fair check gives an unclear result. Two plants may grow by the same measured amount under different light conditions. That does not prove light never matters. It means this comparison did not show the expected difference. The plants, time period or measuring method may limit what the result can tell us. Write the actual result before deciding what to test next.
An honest record can say 'We do not yet have enough evidence to choose'. That is a useful outcome when it stops a confident but unsupported answer. Name the missing information so the next check has a purpose. Repeating the same unfair comparison would add work without fixing its weakness.
A lunch club wants to know whether a tray with a raised edge reduces spilled cups. A student suggests testing the old tray with full cups and the new tray with empty cups. That would almost guarantee an advantage for the new tray, but it would not answer the question fairly. Empty cups cannot spill their contents.
Use the same number of similar cups, the same amount of water and the same safe route for both trays. Ask an adult to supervise a small practice test where spills will not make a slippery path. Record the number of cups that spill for each tray rather than remembering only the most dramatic event.
Suppose three trials with the old tray give three, two and three spills, while three comparable trials with the new tray give one, zero and one. In this supplied case, the new tray spills fewer cups in each paired trial. That supports the claim for these test conditions. It does not establish that spills are impossible or that the result holds for every tray, load and person.
Write the conclusion with its method: 'With equal loads on the same route, the raised-edge tray produced fewer spills in our three trials.' If one trial used a different route, mark it rather than quietly combining it with the others. A useful test makes the route from observation to conclusion visible. Somebody who disagrees can inspect the setup and repeat the check instead of arguing from memory or preference alone.
Thinking more information is always better. Tomato facts that do not compare the two spots add nothing.
Checking only one side. The wall tomatoes were big says nothing about whether they were bigger.
Changing two things at once. Then a difference could come from either.
Question: is the library busier on Saturdays than on Tuesdays?
Question: is the library busier on Saturdays than on Tuesdays?
What does it compare?
State the result of this reading move.
What does it compare?
This records the link just identified: Question: is the library busier on Saturdays than on Tuesdays?
Saturdays with Tuesdays. So both must be counted.
Saturdays with Tuesdays. So both must be counted.
A comparison needs both sides.
State the result of this reading move.
A comparison needs both sides.
This records the link just identified: Saturdays with Tuesdays. So both must be counted.
Check: count everyone coming through the door on four Saturdays and four Tuesdays, the same way each time.
Check: count everyone coming through the door on four Saturdays and four Tuesdays, the same way each time.
About the question, checkable, fair.
Question: does plant food make beans grow taller? Plan: bean A gets plant food on the windowsill; bean B gets none in the cupboard.
Question: does plant food make beans grow taller? Plan: bean A gets plant food on the windowsill; bean B gets none in the cupboard.
How many things differ between A and B?
State the result of this reading move.
How many things differ between A and B?
This records the link just identified: Question: does plant food make beans grow taller? Plan: bean A gets plant food on the windowsill; bean B gets none in the cupboard.
Two: the plant food, and the light.
Two: the plant food, and the light.
If A grows taller, which one did it?
State the result of this reading move.
If A grows taller, which one did it?
This records the link just identified: Two: the plant food, and the light.
Fix: put both on the windowsill, and give only A the plant food.
Fix: put both on the windowsill, and give only A the plant food.
Now only one thing differs.
Identify the task before answering its parts.
A absorbed: {{b0}}
B absorbed: {{b1}}
Difference: {{b2}}
The three labeled spaces ask for different parts of this analysis, so keep their order visible.
Locate the evidence for the first part.
For A, subtract the three remaining spoonfuls from the same starting amount 8.
This is the supplied information that bears on work out a absorbed.
Work out a absorbed.
5
For A, subtract the three remaining spoonfuls from the same starting amount 8.
Work out b absorbed.
7
For B, subtract one remaining spoonful from 8; equal starting amounts permit this comparison.
Work out difference.
2
B absorbed two more in this test. That supports a result under the supplied conditions, not an unlimited claim about all uses.
Write the completed analysis in its original order.
5 / 7 / 2
Read these entries with their labels: Work out a absorbed. / Work out b absorbed. / Work out difference.
Question: is the hill path or the river path quicker to the park? What does it compare?
Question: is the hill path or the river path quicker to the park? What does it compare?
The two paths.
So what must be timed?
What must be kept the same, so the timing is fair?
Question: *does the new crossing make the walk home from the library slower?* Say whether each piece of evidence would help decide. Use these category identifiers: A = would help decide; B = would not help decide. Select the identifier, not the category's words.
| Would it help decide? | |
|---|---|
| Times of the walk for a week before and a week after the crossing opened. | |
| The color of the crossing's stripes. | |
| Whether people say they like crossings. | |
| How long the crossing's light stays red, from the city council's records. |
Two equal-sized towels are each given 11 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
Work out a absorbed.
b0
Subtract what remains from the common starting amount.
Work out b absorbed.
b1
Use the same subtraction for the other towel.
Work out difference.
b2
Compare the resulting absorption amounts.
Two equal-sized towels are each given 15 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
A absorbed: b0
B absorbed: b1
Difference: b2
Two equal-sized towels are each given 9 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
A absorbed: b0
B absorbed: b1
Difference: b2
Two equal-sized towels are each given 10 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
A absorbed: b0
B absorbed: b1
Difference: b2
Two equal-sized towels are each given 13 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
A absorbed: b0
B absorbed: b1
Difference: b2
Lesson test: one question per skill, one attempt each, no hints. Your answers are checked when you submit.
Two equal-sized towels are each given 12 spoonfuls of water. Towel A leaves three spoonfuls; B leaves one. Complete the evidence table: A absorbed ___; B absorbed ___; the larger absorption is ___ spoonfuls more. All other test conditions are the same.
A absorbed: b0
B absorbed: b1
Difference: b2
You can pick the evidence that would settle a question and say why a one-sided check cannot. Say why weighing only the wall tomatoes cannot show they are bigger. Next: choosing between options for a reason.
17. Your turn: the two paths, step 2
So what must be timed?
If the question compares two things, both must be measured the same way.
17. Your turn: the two paths, step 3
What must be kept the same, so the timing is fair?
If the question compares two things, both must be measured the same way.