Scientific Method and Data Lesson Test

Answer: C

Correct answer: The spoon's handle felt hot after five minutes. An observation records what was detected with the senses or an instrument. Feeling that the handle was hot is a direct report; the other statements try to explain why it happened.

• A: This describes a cause for the warming, which makes it an explanation rather than an observation.
• B: This proposes a reason with the word because, so it is an explanation that must be tested.
• C (correct): This reports something the student detected directly by touch, without proposing why it happened.
• D: This is a guess about how heat behaves, not something the student directly sensed or measured.

Answer: D

Correct answer: The height the ball is dropped from. The independent variable is the factor the experimenter deliberately changes. Here the student picks the drop heights of 50, 100 and 150 cm, so drop height is the independent variable.

• A: The landing surface should stay the same throughout, so it is a controlled variable.
• B: Bounce height is the outcome being measured, which makes it the dependent variable.
• C: The same ball is used every time, so ball type is a controlled variable.
• D (correct): The student chooses and changes the drop height on purpose, so it is the independent variable.

Answer: A

Correct answer: One thousand milliliters. The prefix milli- is one thousandth, so 1 L contains 1,000 mL. 1 L = 1,000 mL.

• A (correct): Correct: 1 L = 1,000 mL.
• B: 100 mL is only one tenth of a liter.
• C: 10,000 mL equals 10 L.
• D: 1,000,000 mL equals 1,000 L.

Answer: D

Correct answer: The pitch of the sound each bottle makes. The dependent variable is the outcome that is measured. The student changes the water amount and records the pitch that results, so pitch is the dependent variable.

• A: The student sets the water amount on purpose, so it is the independent variable.
• B: The bottles are identical, so their size and shape are controlled variables.
• C: The same spoon is used every time, so it is held constant as a controlled variable.
• D (correct): Pitch is the result the student measures to see the effect of the water amount, so it is the dependent variable.

Answer: A

Correct answer: 3,600 m. Kilo means 1,000, so 1 km = 1,000 m. Multiply 3.6 by 1,000 by moving the decimal point three places to the right: 3.6 km = 3,600 m.

• A (correct): Since 1 km = 1,000 m, multiplying 3.6 by 1,000 gives 3,600 m.
• B: This divides by 1,000 instead of multiplying, which shrinks the length when it should grow.
• C: This multiplies by 100, as if kilo meant one hundred instead of one thousand.
• D: This moves the decimal point four places instead of three.

Answer: C

Correct answer: Kilogram. The SI base units include the meter for length, the kilogram for mass, the second for time, the kelvin for temperature and the ampere for current. So the base unit of mass is the kilogram.

• A: The newton is a unit of force built from base units, not a base unit of mass.
• B: The gram is a common metric unit, but the SI base unit for mass is the kilogram, which equals 1,000 grams.
• C (correct): The kilogram is the base unit of mass in the International System of Units.
• D: The cubic meter is the SI unit of volume built from the meter, so it measures space, not mass.

Answer: B

Correct answer: Six hundred fifty milliliters. Multiply liters by 1,000:

• A: 6,500 mL equals 6.5 L.
• B (correct): Correct: 650 mL.
• C: 65 mL equals 0.065 L.
• D: 0.065 mL is far smaller than 0.65 L.

Answer: B

Correct answer: The gas had a sharp, sour smell. Qualitative data describe qualities such as color, smell or texture in words. Quantitative data use numbers with units. Only the note about the sharp, sour smell is described without a measurement.

• A: A time of 45 seconds is a measured number with a unit, which makes it quantitative.
• B (correct): This describes a quality in words rather than with numbers, so it is qualitative data.
• C: This note gives a number with a unit, so it is quantitative data.
• D: A temperature reading of 31 °C is numerical, so it is quantitative data.

Answer: D

Correct answer: The twenty plants given plain water. A control group is a set of subjects that does not receive the treatment. The plants given plain water show how beans grow without the plant food, so they are the control group. The matching soil, pot size and light are controlled variables.

• A: These plants receive the treatment being tested, so they are the treatment group.
• B: These are controlled variables held constant across all groups, not a group of subjects.
• C: Plant height is the measured outcome, which is the dependent variable.
• D (correct): These plants do not receive the plant food, so they serve as the baseline for comparison.

Answer: C

Correct answer: Sun exposure changed along with the paint brand, so it is a confounding variable. A confounding variable changes along with the independent variable and could also affect the result. Here sunlight differs between the walls, so the test cannot show whether the brand or the sunlight caused the difference. Both brands should be tested under the same sun exposure.

• A: Fading is the outcome being measured, so it is correctly the dependent variable; the paint brand is the independent variable.
• B: Using one brand on both walls would remove the very factor being tested.
• C (correct): The brands were tested in different amounts of sunlight, so sunlight could explain the difference instead of the paint.
• D: Keeping other factors the same is what makes a test fair; the problem is that sun exposure, a key factor, was not kept the same.

Answer: A

Correct answer: 19.9 mL, 20.0 mL, 20.1 mL. Accuracy means being close to the true value, and precision means repeated readings are close to each other. Readings of 19.9, 20.0 and 20.1 mL are tightly grouped and centered on 20.0 mL, so they are both.

• A (correct): These readings cluster tightly together and sit right at the true value of 20.0 mL.
• B: These readings are widely scattered and their average is not at 20.0 mL, so they are neither precise nor accurate.
• C: These readings agree closely with each other, but they are all about 2.4 mL too high, so they are precise but not accurate.
• D: These readings average 20.0 mL, but they are spread far apart, so they are not precise.

Answer: D

Correct answer: Systematic error; subtract 1 cm from each reading. An error that shifts every reading in the same direction by the same amount is systematic. Averaging more readings does not remove it; correcting for it does, so subtract 1 cm from each length or use an undamaged tape.

• A: The error type is right, but averaging cannot remove an error that shifts every reading by the same amount.
• B: Subtracting 1 cm would work, but an error that always pushes readings the same way is systematic, not random.
• C: Random error scatters readings both high and low, but here every reading is off by the same amount in the same direction.
• D (correct): Every reading is shifted by the same 1 cm in the same direction, so correcting each reading by that amount fixes it.

Answer: C

Correct answer: 2.8 g/mL. The stone's volume equals the rise in water level:

Then density is mass divided by volume:

• A: This divides the volume by the mass, which flips the density formula.
• B: This divides the mass by the starting water level of 25 mL instead of by the volume the stone displaced.
• C (correct): The stone's volume is 55 - 25 = 30 mL, and 84 g divided by 30 mL is 2.8 g/mL.
• D: This divides the mass by the final water level of 55 mL instead of by the change in level.

Answer: D

Correct answer: 10. The median is the middle value after sorting. Sorting gives 3, 5, 10, 10, 12, so the third value, 10, is the median.

• A: This is the middle number of the list as written, before it was put in order.
• B: This is halfway between the smallest and largest values, 3 and 12, which is not the same as the middle value of the sorted list.
• C: This is the mean, found by dividing the total of 40 by 5, not the middle value.
• D (correct): Sorted, the values are 3, 5, 10, 10, 12, and the middle value is 10.

Answer: C

Correct answer: Twenty thousand square centimeters. 1 $m^2$ = ${\left(100cm\right)}^2$ = 10,000 cm²; 2 $m^2$ = 20,000 cm².

• A: 2,000 is ten times too small.
• B: 200 incorrectly applies a single length conversion without squaring.
• C (correct): Correct: 2 × 10,000 = 20,000 cm².
• D: 2,000,000 applies an additional factor of 100.

Answer: B

Correct answer: 25%. Percent change uses the original value as the reference. The change is

L/s, and

so the flow increased by 25%.

• A: This is the new flow as a percent of the old flow, not the percent increase.
• B (correct): The change is 15 L/s, and 15 divided by the original 60 L/s is 0.25, or 25%.
• C: This treats the raw change of 15 L/s as if it were already a percent.
• D: This divides the 15 L/s change by the new value of 75 L/s instead of the original 60 L/s.

Answer: B

Correct answer: 2 °C/min. An average rate is the change in the measured quantity divided by the change in time. The temperature changes by

over

so the rate is

/min. Each 3-minute step adds 6 °C, which agrees.

• A: This divides the final temperature of 38 °C by 9 min without subtracting the starting temperature.
• B (correct): The temperature rises 38 - 20 = 18 °C over 9 min, and 18 divided by 9 is 2 °C/min.
• C: This divides time by temperature change, which flips the rate and its units.
• D: This is the rise for each 3-minute step, not the rise per minute.

Answer: D

Correct answer: Tray Y, with 35% compared with 30%. Groups of different sizes should be compared as percents. Tray X:

or 30%. Tray Y:

or 35%. Tray X had more sprouts in total, but Tray Y germinated at a higher rate.

• A: This compares raw counts even though the trays held different numbers of seeds.
• B: Tray Y's rate is right, but 27 is Tray X's count of sprouts, not its percentage.
• C: This divides Tray X's 27 sprouts by 60, the size of the other tray, instead of by its own 90 seeds.
• D (correct): Tray Y's rate is 21 / 60 = 35%, while Tray X's rate is 27 / 90 = 30%.

Answer: B

Correct answer: 52 mm. Resolution is the smallest change an instrument can show. A ruler marked in millimeters has a resolution of 1 mm, so a length should be reported to the nearest millimeter, such as 52 mm. Extra digits suggest precision the measurement does not have.

• A: Changing to meters does not change the problem; the digits still imply precision far finer than 1 mm.
• B (correct): This reading matches the ruler's resolution of 1 mm.
• C: This equals 52.46 mm written in centimeters, so it still claims precision beyond the 1 mm marks.
• D: Hundredths of a millimeter are far smaller than the ruler's 1 mm marks, so this reading claims precision the ruler cannot provide.

Answer: A

Correct answer: Two point five liters. 1,000 cm³ = 1 L. Therefore 2,500 cm³ = 2.5 L. 2.5 L equals 2,500 cm³.

• A (correct): Correct: 2.5 L equals 2,500 cm³.
• B: 250 L would be 250,000 cm³.
• C: 25 L would be 25,000 cm³.
• D: 0.25 L is only 250 cm³.

Answer: B

Correct answer: Bread molds faster in warm places because warmth speeds up mold growth. A hypothesis is a proposed, testable explanation. The statement that warmth speeds up mold growth explains the pattern and could be tested; the other statements are a procedure, an observation and an opinion.

• A: This records what was seen, so it is an observation.
• B (correct): This proposes a testable explanation for why bread molds at different speeds.
• C: This describes a procedure for collecting data, not a proposed explanation.
• D: This is an opinion, not a testable explanation.

Answer: A

Correct answer: Draw names to decide which volunteers get the lotion. Letting volunteers choose can create groups that already differ, for example in skin care habits. Random assignment, such as drawing names, uses chance to decide who gets the lotion, so hidden differences are spread evenly between the groups.

• A (correct): Random assignment spreads hidden differences evenly between the groups, so neither group is favored.
• B: This changes who is studied but still lets personal habits decide who gets the treatment.
• C: Choosing subjects by skin type puts a built-in difference between the groups, which can bias the results.
• D: With no untreated group, there is no baseline to compare the lotion against.

Answer: C

Correct answer: Thirty-six degrees Fahrenheit. A change of 20 °C scales by $\frac{9}{5}$: 20 × $\frac{9}{5}$ = 36 °F. Do not add the +32 offset to a temperature change. a 20 °C rise equals a 36 °F rise.

• A: 52 °F incorrectly adds 32 to a 20-degree Celsius difference.
• B: 86 °F confuses an absolute Fahrenheit temperature with a difference.
• C (correct): Correct: a 20 °C rise equals a 36 °F rise.
• D: 20 °F ignores the size difference of the degrees.

Answer: D

Correct answer: Look at eye level and read the bottom of the curved surface. To avoid parallax error, the eye must be level with the liquid surface. For water, the reading is taken at the bottom of the curved surface, called the meniscus.

• A: Reading from above causes parallax error, and the top edge is not the correct reference point for water.
• B: The edges where the water climbs the glass are higher than the true level, so this reads too high.
• C: The bottom of the curve is the right point, but viewing from below causes parallax error.
• D (correct): Viewing at eye level avoids parallax, and the bottom of the meniscus marks the correct volume.

Answer: D

Correct answer: Grow 15 separate seedlings in each type of soil. Measuring one plant many times only checks the reading of that single plant. With one seedling per group, an unusually strong or weak plant could produce the whole difference. Using many independent seedlings in each group is replication, which makes the comparison reliable.

• A: A finer ruler improves resolution, but the main weakness is having only one plant per group.
• B: Extra digits suggest precision but do nothing to fix a sample of one plant per group.
• C: More readings of the same plant only check the measurement of that one plant; they do not add independent trials.
• D (correct): Many independent seedlings per group show whether a difference is consistent rather than due to one unusual plant.

Answer: A

An observational survey can show that two things are correlated, but correlation alone does not prove causation. Students who eat breakfast may also sleep more or have other habits that affect scores, so a controlled study would be needed to show cause.

• A (correct): This states the correlation the survey found while recognizing that a third factor may drive both.
• B: This reverses the direction and still claims a cause that the survey cannot show.
• C: The survey found that the two tend to change together; a few exceptions do not erase an overall connection.
• D: A large sample makes the pattern more trustworthy, but a survey is not a controlled experiment, so it cannot rule out other causes.

Answer: A

Correct answer: About 33%. Percent change is the change divided by the original value for that period. In the second year the original value is 60, and the change is

So 20 / 60 is about 0.333, an increase of about 33%. The first year's drop was 25% because its reference was 80.

• A (correct): The second year starts at 60, so the 20-frog rise is 20 / 60, or about 33%.
• B: This is 80 ÷ 60, the new value as a percent of the old one; only the part above 100% is the increase.
• C: This divides the 20-frog change by 80, but 80 is the starting value only for the first year's decrease.
• D: The population ended where it began after two years, but in the second year alone it rose by 20 frogs.

Answer: C

Correct answer: 60,000 cm³. The volume is

Because 1 m = 100 cm, a cubic meter holds 100³ = 1,000,000 cm³:

As a check, 50 cm × 40 cm × 30 cm = 60,000 cm³.

• A: This converts 0.06 m³ with the area factor of 10,000 instead of the volume factor of 1,000,000.
• B: This misplaces the decimal in the volume, using 0.6 m³ instead of 0.06 m³ before converting.
• C (correct): The volume is 0.06 m³, and 0.06 times 1,000,000 is 60,000 cm³; this also equals 50 cm times 40 cm times 30 cm.
• D: This treats 1 m³ as 1,000 cm³; the box actually holds 60 L, not 60 cm³.

Answer: A

Correct answer: The median, 9 h, because the 44 h value pulls the mean up to 16 h. Sort the values: 8, 9, 9, 10, 44 h. The median is 9 h. The mean is

h, pulled up by the outlier of 44 h. Because the outlier is real it should be reported, but the median better describes a typical battery.

• A (correct): Sorted, the values are 8, 9, 9, 10 and 44 h, so the median is 9 h, and it is not dragged upward by the one extreme value.
• B: This takes the middle of the list as recorded, without sorting it first.
• C: The mean of 80 / 5 = 16 h is higher than four of the five results, so the outlier makes it a poor picture of a typical battery.
• D: The range of 44 - 8 = 36 h measures spread, not a typical value.

Answer: B

Correct answer: Town A, with a rate of 3.5 per 1,000. Divide each number of cases by the population and multiply by 1,000. For Town A,

For City B,

For Town C,

Town A has the highest rate even though it has the fewest cases.

• A: Town A has the highest rate, but 21 / 6,000 × 1,000 equals 3.5, not 35; the decimal point was misplaced.
• B (correct): Town A's rate is 21 / 6,000 × 1,000 = 3.5, which is higher than Town C's 3.0 and City B's 2.5.
• C: City B has the most cases, but its rate is only 100 / 40,000 × 1,000 = 2.5 per 1,000 people.
• D: Town C's rate is correctly 3.0 per 1,000, but Town A's rate is higher.

Answer: B

Correct answer: 122 °F. First find the final Celsius reading:

Then convert the reading, which does use the offset:

As a check, 35 °C is 95 °F, and a 15 °C rise is

giving

• A: This adds the 32 offset twice, once to the starting reading and again to the temperature change.
• B (correct): The final temperature is 35 + 15 = 50 °C, and 1.8 × 50 + 32 = 122 °F.
• C: This multiplies 50 °C by 1.8 but forgets to add the 32 offset for a temperature reading.
• D: This converts 35 °C to 95 °F and then adds 15 without converting the Celsius change to Fahrenheit degrees.

Answer: C

Correct answer: Under these greenhouse conditions, the fertilized tomato plants grew taller over six weeks. A sound conclusion stays within the conditions tested: one tomato variety, a 24 °C greenhouse and six weeks of growth, with height as the measurement. Claims about all plants, all climates, harvests or week 20 go beyond what the data show.

• A: Only one tomato variety in one greenhouse was tested, so this claim reaches far beyond the conditions studied.
• B: This extrapolates well beyond the six weeks measured, where growth conditions and rates may change.
• C (correct): This matches the measured difference and stays within the plants, setting and time span that were tested.
• D: The test measured plant height for six weeks, not harvest, and a single test cannot prove an always statement.

Answer: B

Correct answer: Field B's yield is about 9.5% higher than Field A's. Read the real values from the axis, not the bar sizes, because the baseline is 80 kg rather than 0.

Field B's yield is only about 9.5% higher, even though its bar looks three times as tall.

• A: This compares the bar heights by eye; the bars only measure 4 kg and 12 kg above the 80 kg baseline, not the full yields.
• B (correct): The difference is 92 minus 84, or 8 kg, and 8 divided by the reference value 84 is about 0.095, a 9.5% increase.
• C: The 8 is a difference in kilograms, not a percent; it must still be divided by the original value of 84 kg.
• D: This divides the 8 kg difference by 92 instead of 84, using the wrong reference value for an increase from Field A.

Answer: D

Correct answer: 0.000002 m. Micro (µ) means one millionth, so 1 µm = 0.000001 m. Then 2 µm = 2 × 0.000001 m = 0.000002 m, which is the decimal point moved six places to the left.

• A: This treats µ (micro, one millionth) as m (milli, one thousandth).
• B: This multiplies by one million instead of dividing; micro makes a unit smaller, not larger.
• C: This moves the decimal point only five places instead of six.
• D (correct): Micro means one millionth, so 2 µm is 2 millionths of a meter, or 0.000002 m.

Answer: A

Correct answer: It is a negative control. A negative control gets no treatment and is expected to show no effect from it. Comparing the treated dishes with this sterile-water dish shows whether the disinfectant made any difference.

• A (correct): It receives no treatment and is expected to show ordinary growth, giving a baseline for what happens without the disinfectant.
• B: A positive control uses something already known to work, such as a proven disinfectant; sterile water is not expected to stop growth.
• C: The dependent variable is the measured outcome, such as the amount of bacterial growth, not a dish or group.
• D: Controlled variables are factors held constant across all dishes, such as temperature; this dish is a comparison group.

Answer: B

A hypothesis explains why, while a prediction states the specific result you expect to observe if the hypothesis is right. The if-then statement naming the setup and the expected outcome is the prediction.

• A: This proposes why something happens, so it is a hypothesis, not the specific expected result of a planned test.
• B (correct): This states the specific result expected in a planned test, in if-then form, which is what a prediction does.
• C: This is a testable question; it asks something but does not state what result is expected.
• D: This describes results that were already seen, so it is an observation, not a prediction.

Answer: D

Correct answer: Have the nurses rate itching without knowing which patients used the cream. Observer bias happens when what researchers expect affects what they record. In a blind study the people measuring results do not know which subjects received the treatment, so their expectations cannot shape the ratings.

• A: Repeated ratings by people who still know the groups can repeat the same bias; averaging does not remove it.
• B: A larger sample makes averages more reliable but does not stop nurses from seeing what they expect.
• C: Self-selection makes the groups less fair; it does nothing about the nurses' expectations.
• D (correct): Blinding the people who record results keeps their expectations from influencing what they record.

Answer: C

Correct answer: 4 m/s. On a distance-time graph, the slope is the speed. Divide the change in distance by the change in time.

• A: This divides 38 m by 10 s as if the line started at the origin; the graph passes through 6 m at 2 s.
• B: This uses only the first point, 6 m divided by 2 s, instead of the change between the two points.
• C (correct): Slope equals the change in distance, 32 m, divided by the change in time, 8 s, which gives 4 m/s.
• D: This divides the change in time by the change in distance, which flips the rate upside down.

Answer: A

Interpolation estimates a value between measured points and is usually fairly safe. Extrapolation goes beyond the measured range, here from week 6 to week 30, and is riskier because conditions such as the plant's growth limit may change.

• A (correct): Week 4.5 lies between measured points, while week 30 is far beyond the data, where growth conditions may change.
• B: This reverses the terms; estimating between measured points is interpolation, and going beyond them is extrapolation.
• C: A steady trend inside the measured range does not guarantee it continues far outside it; the plant may stop growing.
• D: Both estimates use the same data; the farther an estimate goes beyond the tested range, the less trustworthy it is.

Answer: C

Correct answer: 15%. Percent change uses the original value as the reference.

• A: This reports the 6 L drop as a percent without dividing by the original value.
• B: This divides the 6 L drop by the new value, 34 L, instead of the original 40 L.
• C (correct): The drop is 6 L, and 6 divided by the original 40 L is 0.15, a 15% decrease.
• D: This is 34 divided by 40, the new use as a fraction of the old, not the amount of decrease.

Answer: B

Correct answer: 7.8 g/mL, so it sinks in water. Convert to matching units: 0.39 kg = 390 g, and the volume is the rise in level, 1.25 L minus 1.20 L = 0.05 L = 50 mL.

This is much more than water's density of about 1 g/mL, so the part sinks.

• A: This uses the final water level of 1,250 mL as the part's volume instead of the 50 mL rise.
• B (correct): The mass is 390 g and the volume is 0.05 L, or 50 mL, so the density is 390 g divided by 50 mL, which is greater than water's 1 g/mL.
• C: This leaves the mass in kilograms, dividing 0.39 by 50 mL, instead of converting it to 390 g.
• D: This divides the volume by the mass, 50 by 390, which inverts the density formula.

Answer: A

The proven antibiotic is a positive control: it should stop growth if the method works. Because it failed, the test cannot show an effect even when one exists, so the method must be checked before the new antibiotic can be judged.

• A (correct): When the positive control fails, the experiment has not shown it can detect an effect, so the new drug's result means little.
• B: This ignores the failed positive control; if a proven antibiotic did not work either, the setup itself may be at fault.
• C: Heavy growth without antibiotic is exactly what a negative control should show, so it gives no sign of a problem.
• D: Both failed equally, which says nothing about the new drug's strength because the test could not detect any effect.

Answer: C

Correct answer: 2.5 g/mL. A calculated value should not look more precise than the measurements used to make it. The mass has three significant figures and the volume has two, so the density is reported with two: 2.4918033 rounds to 2.5 g/mL.

• A: Copying every calculator digit suggests far more precision than the measurements support.
• B: This keeps three significant figures, but the volume measurement justifies only two.
• C (correct): The volume, 6.1 mL, has only two significant figures, so the answer should be rounded to two significant figures.
• D: This rounds to one significant figure, throwing away precision the data actually support.

Answer: D

Correct answer: A well-tested explanation that ties together many observations. In science, a theory is a broad, well-tested explanation, such as plate tectonics, that ties together many observations. A law describes a pattern, a hypothesis is a testable proposed explanation, and all of them can be revised if new evidence requires it.

• A: This is the everyday meaning of theory; in science an untested idea is closer to a hypothesis.
• B: Describing a pattern is the job of a scientific law, and both laws and theories can be refined by new evidence.
• C: One experiment cannot prove an idea; theories build confidence through many repeated tests.
• D (correct): A scientific theory has survived repeated attempts to disprove it and explains why many observations happen.