Quiz 2 — The Scientific Method

The Guide

Six stations, and the question that follows them

The GED will not ask you to recite the scientific method. It will hand you somebody's experiment and ask what went wrong with it, or which part is the control, or what the results actually show. To answer those questions you need the parts by name.

The dark red arrows on the outside run forward, and the last one closes the loop: a conclusion usually raises the next question. The teal arrows on the inside run backward, because you can return to an earlier step at any point. A result that makes no sense often means the setup was wrong, not the world. Real investigation moves both ways. The circle is the order you learn it in.

The six stations

Question: Something you noticed and want to explain. It has to be narrow enough that a test could answer it.
Hypothesis: A possible answer, stated plainly enough that a test could show it is wrong. A hypothesis is a statement, not a question — this is worth a point on the test all by itself.
Variables and Controls: The one thing you change on purpose is the independent variable. The thing you measure is the dependent variable. Everything else you hold the same, and those are the constants. A control group gets no treatment, so you have something to compare against.
Test: Do it. Then do it again. One trial tells you very little, because a single result can come from chance or from a mistake.
Data: What you actually recorded, written down before you decide what it means.
Conclusion: What the data supports, and no more. "The hypothesis was wrong" is a real conclusion, not a failed experiment.

The outer ring. A conclusion is not yet knowledge. It becomes knowledge when people who were not there the first time can get the same result — the scientist repeating her own work, another lab running the same test, another team asking the same question a different way. Run it once and you have a story. Run it again and you have a finding. Run it in someone else's hands and you have knowledge.

Two words the test will use. A measurement is reliable when you get the same reading each time you repeat it. It is valid when it measures the thing you say it measures. A bathroom scale that reads ten pounds heavy is perfectly reliable and not valid at all: the same wrong number, every time.

The question that comes up most. "How could this investigation be improved?" Four answers cover nearly every case: run more trials, use a larger group, add a control group, and change only one thing at a time. If two things changed at once, no result can tell you which one mattered.

Worked Examples

Two questions, worked through

Passage

A baker wanted to know whether adding a teaspoon of vinegar makes bread rise higher. She baked six loaves with vinegar and six without. Every loaf used the same flour, the same yeast, the same amount of water, the same oven temperature, and the same rising time. She measured the height of each loaf when it came out.

Example 1. Name the independent variable, the dependent variable, and two constants.

Ask three questions in order. What did she change on purpose? The vinegar — that is the independent variable. What did she measure? The height of the loaves — that is the dependent variable. What did she deliberately keep the same? Flour, yeast, water, oven temperature, rising time — those are the constants.

The constants are not filler. They exist so that when the heights differ, vinegar is the only thing left that could have caused it.

Example 2. The vinegar loaves rose about 1 cm higher on average. What conclusion is supported, and what would make it stronger?

Supported: in this batch, with this flour and this yeast, the loaves with vinegar rose slightly higher. Not supported: vinegar makes any bread rise higher anywhere. Six loaves in one kitchen is a start, not a settled fact.

To make it stronger: bake more loaves, repeat on another day, and have a second baker try it in a different kitchen. That last step is the outer ring — it is what separates an interesting result from a reliable one.

The Quiz

Ten questions

Answer all ten, then press the button at the bottom. Nothing is timed.

Passage A — questions 1 to 4

A nurse at a community clinic wanted to know whether a ten-minute stretching routine reduces lower back pain in people who stand all day at work. She recruited 60 grocery cashiers. She randomly assigned 30 of them to do the routine every morning before their shift. The other 30 were asked to change nothing about their day.

All 60 rated their back pain on a scale from 0 to 10 at the end of each week for six weeks. Everyone in the study worked for the same grocery chain and worked shifts of similar length.

1.Which of these is the best hypothesis for this study?

AStretching is good for everyone.
BCashiers who do the ten-minute routine will report less back pain than cashiers who do not.
CDoes stretching reduce back pain in cashiers?
DStanding all day causes back pain.

2.What is the independent variable?

AThe weekly pain rating from 0 to 10
BThe number of cashiers in the study
CThe length of the work shift
DWhether the cashier does the stretching routine

3.What is the dependent variable?

AThe weekly pain rating
BThe stretching routine
CThe six weeks the study lasted
DThe grocery chain

4.Which group is the control group?

AAll 60 cashiers
BThe 30 who did the stretching routine
CThe 30 who were asked to change nothing
DThe nurse who ran the study

Passage B — questions 5 to 7

A student wanted to find out which of two brands of battery lasts longer in a flashlight. He put Brand A in his flashlight, switched it on indoors, and timed how long until the light went out: seven hours.

The next day he put Brand B in a different flashlight, left it switched on out on the porch overnight in the cold, and timed it: five hours. He concluded that Brand A is the better battery.

5.What is the biggest problem with this test?

AHe should have tested three brands instead of two.
BMore than one thing was different between the two tests, so the brand may not be what caused the difference.
CHe should have measured in minutes instead of hours.
DA flashlight cannot be used to test batteries.

6.Which change would most improve this investigation?

ABuy a more expensive flashlight.
BTest Brand A a second time.
CAsk friends which brand they prefer.
DTest both brands in the same flashlight at the same temperature, and repeat the test several times.

7.Which conclusion do his results actually support?

AVery little, because the two batteries were not tested under the same conditions.
BBrand A lasts longer than Brand B in all conditions.
CCold temperatures have no effect on batteries.
DBrand B batteries are defective.

Passage C — questions 8 and 9

In 1989 two chemists called a press conference to announce that they had produced nuclear fusion in a jar of water at room temperature. If true, it would have been one of the most important results of the century.

Laboratories around the world immediately tried to repeat the experiment. A few reported unexplained heat. Most found nothing at all. Within a year the claim had been widely rejected.

8.Why did laboratories around the world try to repeat the experiment?

ATo decide who should receive the credit for it.
BBecause the law requires every experiment to be repeated.
CBecause a result is accepted only when other people, working separately, can obtain it too.
DBecause the announcement was obviously false from the start.

9.A reader says, "This shows the two chemists lied." Does the passage support that statement?

AYes, because nobody else could get their result.
BNo. The passage says others could not repeat the result. It says nothing about whether the chemists lied.
CYes, because they announced it at a press conference.
DNo, because a few laboratories did report unexplained heat.

Question 10

A kitchen thermometer reads exactly three degrees too high every single time it is used.

10.How would you describe this thermometer?

ANeither reliable nor valid
BValid but not reliable
CReliable but not valid
DBoth reliable and valid

Send this line to your teacher

The line records which questions you missed and which answer you chose. That is more useful to your teacher than the score, because it shows where a question went wrong. If a question felt unclear even though you got it right, add its number with a question mark — for example 5? — before you send it.

Score ______ / 10 Missed — write the question number and the letter you chose:
______________________________________________________________

The Key

Answers, and the trap in each one

1. B. It is a statement, it names both groups, and a six-week study could show it to be wrong. That is everything a hypothesis needs. C is the same idea with a question mark, and that one punctuation mark is the whole difference: a question starts the wheel, a hypothesis is the next station. A cannot be tested as written. D may well be true, but it is not what she set out to test.

2. D — whether the cashier does the stretching routine. It is the one thing she changed on purpose, and the one thing that differs between the two groups. A is what she measured, which makes it the dependent variable. Swapping these two is the single most common mistake on this topic. Independent is what you do; dependent is what you watch.

3. A — the weekly pain rating. It is the measurement. Its value may depend on which group the cashier is in, and that dependence is where the name comes from. C and D are things she held steady, which makes them constants.

4. C — the 30 asked to change nothing. The control group is the comparison. Without it, a drop in pain over six weeks could be the stretching, or the season, or simply the fact that people were paying attention to their backs. B is the treatment group. If you picked it, you may be reading "control" as "the group being controlled." The control group is the one left alone.

5. B — more than one thing was different. Different brand, different flashlight, different temperature. When three things change at once, the result cannot tell you which one mattered. Cold alone could account for the whole gap. A sounds scientific — more brands, more data — but adding a third brand to a broken comparison just gives you three unusable numbers.

6. D — same flashlight, same temperature, several trials. This is the standard repair: change one thing at a time, hold the rest steady, and run it more than once. B is genuinely half right, which is what makes it dangerous. Repeating the test is good, but repeating only Brand A leaves the comparison just as broken as before.

7. A — very little. "Very little" is an uncomfortable answer, and it is often the correct one. A badly designed test does not produce a small conclusion; it produces no conclusion. B is the student's own conclusion, restated with the word all added. Notice how a claim grows as it travels: seven hours in one living room becomes a fact about every condition on earth.

8. C — because a result is accepted only when others can obtain it too. This is the outer ring of the wheel, and it is the part that makes science different from an announcement. D reads the ending back into the beginning. When the labs started work, nothing was obvious. That is exactly why they ran the tests.

9. B — no, the passage says nothing about lying. Failing to repeat a result and lying about a result are different things. Honest people get results that do not hold up; it happens constantly, and the ring is how it gets caught. D reaches the right verdict for the wrong reason, and the test will offer you that trade all day. The answer is not "no, because of this other evidence." It is "no, because the passage never addressed it."

10. C — reliable but not valid. Reliable, because it gives the same reading every time. Not valid, because the reading is not the temperature. B has the words in the wrong order. One way to keep them straight: reliable is about repeating, valid is about truth.

Your Score

What the number means

8 to 10	Solid. Check topic 2 on your map and go on to Quiz 3.
6 or 7	Close. Read the whole key, then take this again in a few days before you check the box.
5 or fewer	Worth real time. This vocabulary appears in questions all the way through the test, on life science and physical science alike. Draw the wheel from memory, then work the two examples again on paper.

Which ones you missed tells you what to do next. Misses on 2, 3, 4, or 10 are vocabulary — the words are learnable in an afternoon, and drawing the wheel by hand fixes most of it. Misses on 5, 6, or 7 mean you did not spot a broken comparison, which is worth practicing, since the test asks about it constantly. Misses on 9 mean a statement slipped past you that went further than the evidence. That last one is the deepest habit this whole series is trying to build.

The gallery for this quiz

Two pictures of Mars belong here, side by side. The first is one of Percival Lowell's drawings from around 1895: a globe crossed by fine straight lines he called canals, which he believed had been dug by intelligent beings. He had a good telescope on a good mountain, he drew what he saw night after night, and the lines stayed put. Other astronomers looked and could not find them. Lowell said they simply had worse conditions.

The second is the photograph Mariner 4 sent back in 1965, on the first close pass any spacecraft made of Mars. There were no canals. There had never been any canals.

Images to be placed at deployment. Lowell's drawings are in the public domain by age and are available through the Internet Archive; Mariner 4 photographs are NASA work and free to use with credit. Nobody in this story was dishonest. A careful man saw what he expected to see, and it took a camera on a different instrument to settle it — which is the outer ring of the wheel, doing its work over seventy years.