Command of Evidence — Quantitative — Topic practice
16 exercises · 16 automatically checked · Untimed
Instructions and review guidance
16 questions · Shuffled order · Progress saved locally when available
Identify the evidence for each answer and the specific flaw in its nearest competitor. Complete the four written drills in the lesson before this practice set.
Guide question labels stay the same when the order changes. Check answers when you are ready to review.
Saved on this browser and device; clearing browser data removes progress.
The drill
Your practice is saved on this device.
Question 5
Guide question 4.05
Foundation
In a hypothetical exhibit study, visitors saw either standard labels or simplified labels. Researchers measured the percentage who read a label at three observation times. They claim that simplified labels had a consistently higher reading rate and that the advantage did not change across observations.
Label reading over three observations
Separate groups of visitors saw the two label versions.
Which statement most directly supports the claim?
Why this answer
Constant gap across observations
Correct choice: Simplified-label reading exceeded standard-label reading by 20 percentage points at every observation.
The paired differences are 40 - 20,50 - 30, and 60 - 40: all 20 percentage points. C establishes a positive, unchanged advantage.
A: The final maximum is accurate but does not establish the advantage at earlier observations.
B: The endpoint gains are accurate, but equal total gains alone do not show an unchanged gap at every intermediate observation.
D: Both rates increase by 20 points, so the stated two-to-one change comparison is false.
If you missed it: Compare the two series at every observation named in the claim.
Three hypothetical hatcheries report results for one batch of eggs each. A researcher states that Hatchery B had the highest hatching rate, even though Hatchery A produced the most hatchlings.
Hatching outcomes
Hatchery
Eggs
Hatched
A
200
120
B
100
80
C
50
20
Each hatchling came from one egg in the reported batch.
Which statement best supports the researcher's statement?
Why this answer
Largest count versus highest success rate
Correct choice: B hatched 80% of its eggs, versus A's 60% and C's 40%; hatchling totals were A 120, B 80, and C 20.
The hatching rates are A: 120/200 = 60%; B: 80/100 = 80%; C: 20/50 = 40%. A nevertheless has the largest hatchling count.
B: This establishes the count ranking but omits the rate comparison.
C: B has 20 unhatched eggs and A has 80, but A still produces more hatchlings.
D: The facts about C are true, but 100 is not halfway between 200 and 50; the statement also omits rates.
If you missed it: Calculate success divided by attempts before comparing success rates.
A hypothetical park redesigned its path signs. A planner argues that the new layout narrowed the difference between morning and afternoon visitors in choosing the intended path. The figure reports the percentage choosing that path under each layout.
Choice of intended path
Percentages are calculated separately within each time and layout group.
Which statement most directly weakens the planner's argument?
Why this answer
Use unchanged gaps to weaken a claim
Correct choice: Both groups gained 20 percentage points, leaving their gap unchanged at 20 points.
The old gap is 50 - 30 = 20 points; the new gap is 70 - 50 = 20. Both groups improve, but the gap does not narrow.
A: A remaining afternoon advantage is compatible with either a smaller or an unchanged gap; the statement does not compare gaps.
B: Morning improvement is real but does not show whether afternoon improvement was smaller, equal, or larger.
C: The baseline values are true but cannot establish the new gap.
If you missed it: For a claim about narrowing, calculate the gap before and after.
In a hypothetical planting trial, researchers measured the percentage of seedlings established under two growing methods. They argue that the new method moved from below the conventional method to above it between the second and third measurements.
Seedling establishment
Equal-size groups of seedlings were followed under each method.
Which statement best supports the argument?
Why this answer
Locate a reversal in ordering
Correct choice: The new method was below conventional at measurement 2, 40% versus 50%, but above it at measurement 3, 60% versus 50%.
At measurement 2, new is 10 points lower. At measurement 3, new is 10 points higher. These paired observations locate the ordering reversal in the specified interval.
A: This describes growth in the new method but does not compare it with conventional at either relevant time.
C: An unchanged conventional rate does not by itself establish that the new method passed it.
D: This true change occurs before the interval in the claim and does not establish a reversal.
If you missed it: To verify overtaking, show the ordering on both sides of the stated interval.
A student studying three hypothetical poetry anthologies argues that translated poems made up a steadily increasing share of the contents from one edition to the next. Each poem is classified as either translated or not translated.
Contents of three anthology editions
Edition
All poems
Translated poems
1
100
40
2
200
60
3
200
80
Translated poems are included in the total for each edition.
Which statement most directly challenges the student's argument?
Why this answer
Distinguish increasing counts from increasing shares
Correct choice: From edition 1 to edition 2, translated poems increased from 40 to 60, but their share fell from 40% to 30%.
The shares are 40/100 = 40%,60/200 = 30%, and 80/200 = 40%. The initial decline contradicts a steadily increasing share.
B: This accurately supports an increase in the final interval, but it does not address the earlier decline.
C: The translated-poem count doubled, but the total poem count also doubled. Counts alone do not establish rising shares.
D: The within-edition majority is true but does not compare shares across editions.
If you missed it: Write each edition's translated count over its total before evaluating the trend.
A hypothetical filtration test compares two filters under three water-flow conditions. A technician claims that Filter P removes a greater percentage of particles than Filter Q at every tested flow level.
Particle removal by flow level
Both filters were tested at each of the three flow levels.
Which finding most directly weakens the technician's claim?
Why this answer
Find a counterexample to an across-condition claim
Correct choice: At high flow, Filter Q removed 70% of particles, exceeding Filter P's 60%.
High flow supplies a direct counterexample: Q outperforms P, 70% to 60%. P therefore does not outperform Q at every tested level.
A: P's maximum is true but does not establish its superiority across all flow levels.
B: P's decline is true, but P could decline and still outperform Q. The claim requires between-filter comparisons.
D: This supports P's advantage at low flow and does not weaken the claim.
If you missed it: For "every," compare the groups within each condition and look for one relevant exception.
Observers counted resting birds simultaneously at two nearby sites during five hypothetical surveys. A researcher proposes that the pattern is consistent with a shift in where birds were observed, rather than a decline in the combined number observed at the two sites. The counts do not identify individual birds.
Simultaneous bird counts
Both sites were surveyed simultaneously; individual birds were not identified.
Which statement most directly supports the researcher's proposal?
Why this answer
Relevant combined totals and opposing local trends
Correct choice: The combined count remained 40, while the two sites' counts moved in opposite directions.
Each pair sums to 40. A's increases coincide with B's decreases, and the later movement reverses. This supports the proposed observational pattern without proving that particular birds moved.
A: A local peak is accurate but does not address the combined count.
C: B's endpoint recovery is accurate but leaves out A and the combined pattern.
D: The rank reversals are accurate but, by themselves, do not establish the unchanged combined count.
If you missed it: When the claim concerns a combined population, inspect totals as well as each local series.
A hypothetical transcription project used Method P for 100 tasks and Method Q for 100 tasks. The methods were assigned different mixes of simple and complex tasks. Overall, P completed 83% successfully and Q completed 43% successfully. A manager uses these overall rates to conclude that P is the more effective method.
Which finding most strongly challenges the manager's reasoning?
Why this answer
Composition can distort an overall comparison
Correct choice: Q had the higher success rate within both difficulty categories, while P received many more simple tasks.
Q exceeds P on simple tasks, 95% versus 90%, and complex tasks, 30% versus 20%. P's workload is 90% simple, versus Q's 20%. The overall ranking reflects this composition difference.
A: This repeats the overall difference; it does not test whether task mix explains that difference.
B: Equal total sample sizes do not imply comparable difficulty mixes.
C: Difficulty matters for P, but this fact alone does not compare methods within difficulty categories.
If you missed it: Before trusting an overall rate, compare relevant subgroups and their proportions in each total.
In a hypothetical randomized study, two groups practiced a memory task, but only one received an additional training exercise. A researcher claims that the trained group's advantage over the comparison group grew during the first two days and then remained unchanged through day 3.
Memory scores during training
Groups were randomly assigned and completed the same memory assessment.
Which statement most directly supports the claim?
Why this answer
Distinguish a growing effect from a plateau
Correct choice: The between-group gap was 0, 5, 10, and 10 percentage points on days 0 through 3.
The paired differences are 0, 5, 10, and 10. They increase across the first two intervals and remain constant in the last interval, matching both parts of the claim.
A: The final gap is accurate but does not show when the advantage grew.
B: The endpoint gains are accurate but do not establish the timing of growth or a final plateau.
C: Both groups' improvement and plateau are accurate, but the statement does not establish that their gap grew during each of the first two days.
If you missed it: For a claim about the development of an advantage, build a short sequence of between-group differences.
A hypothetical exhibit compares its usual labels with visual explanations and audio explanations. Designers prefer a version that improves comprehension in both language-fluency groups while narrowing their comprehension gap the most. Visitors were randomly assigned to a version within each fluency group.
Comprehension by explanation format
Fluency refers to the language used in the exhibit.
Which statement best supports choosing the audio explanations under these criteria?
Why this answer
A smaller gap while both groups improve
Correct choice: Audio raised both groups' scores and reduced the gap to 10 points, versus 30 with visuals and 40 with usual labels.
Audio raises less-fluent scores from 30% to 65% and more-fluent scores from 70% to 75%. Its 10-point gap is smaller than the visual gap of 30 and the usual gap of 40.
A: The more-fluent maximum is true, but choosing the highest endpoint in that group is not the stated goal.
C: The less-fluent comparison favors audio but omits more-fluent improvement and the size of the gap.
D: This establishes gains for one group under both versions, not which version best satisfies both criteria.
If you missed it: Check every criterion: two improvements and the smallest remaining gap.
In a hypothetical controlled experiment, plants were randomly assigned to combinations of aphids and predatory insects. Researchers propose that predators improve plant growth mainly by reducing aphids, rather than by directly stimulating growth when aphids are absent. Aphid counts were measured at the end of the experiment.
Aphids and plant growth
Aphids introduced?
Predators?
Final aphids
Growth (mm)
Yes
No
80
30
Yes
Yes
20
50
No
No
0
50
No
Yes
0
50
Aphid counts and height gains are group means; other conditions were held constant.
Which finding most directly supports the proposed mechanism?
Why this answer
Evidence for an indirect biological mechanism
Correct choice: Predators reduced aphids and increased growth when aphids were introduced, but did not increase growth when aphids were absent.
With aphids introduced, predators lower the final aphid count from 80 to 20 and raise growth from 30 to 50 millimeters. Without aphids, growth stays at 50 regardless of predators. Together, these comparisons support the indirect mechanism.
B: This addresses the lack of a direct benefit without aphids but omits the predator effect when aphids are present.
C: This shows fewer aphids but does not connect that reduction to plant growth.
D: This supports an aphid-related growth difference but does not evaluate the effect of predators.
If you missed it: For a proposed indirect mechanism, connect the intervention, intermediate change, and outcome; check the condition where the mechanism should be absent.
A hypothetical study tests reminders during puzzles of three difficulty levels. A researcher claims that the reminder benefit becomes smaller as difficulty rises when measured in percentage points, but is the same across difficulties when measured as a relative increase over the no-reminder completion rate.
Puzzle completion with reminders
Completion rates use all attempted puzzles within each condition as the denominator.
Which statement best supports the claim?
Why this answer
Percentage-point effects versus proportional effects
Correct choice: The gains were 30, 20, and 10 points, respectively; each was a 50% relative increase.
The gains are 90 - 60 = 30,60 - 40 = 20, and 30 - 20 = 10 points. Relative to their baselines, 30/60,20/40, and 10/20 all equal 50%.
A: These endpoint rates are true but omit the no-reminder baselines needed to measure benefit.
B: Improvement at every level is true but does not compare benefit sizes in either unit.
D: The between-difficulty drops are accurate but do not directly compare reminder gains or their proportional sizes.
If you missed it: Calculate each intervention-minus-baseline difference first; then divide each difference by its own baseline.
In a hypothetical study, one community center introduced appointment reminders immediately after week 1; another did not. The centers already differed in attendance before reminders began. A researcher argues that the later data are consistent with an additional attendance improvement at the reminder center, beyond its earlier advantage.
Appointment attendance
Reminders began immediately after week 1; comparison center used no reminders.
Which observation most directly supports this interpretation?
Why this answer
Account for an existing gap and a background trend
Correct choice: The attendance gap was 10 points in both pre-introduction weeks, then widened to 20 and 30 points afterward.
Before reminders, the gap is 10 points at weeks 0 and 1. Afterward it becomes 20 and then 30. The widening supports an additional improvement, although this nonrandomized comparison does not by itself establish causation.
A: An advantage both before and after could occur without any additional improvement.
C: The comparison center's plateau is relevant context but alone does not establish the reminder center's additional gain.
D: The final maximum does not account for the earlier advantage or the comparison trend.
If you missed it: Separate a preexisting difference from a difference that emerges after the intervention.
In a hypothetical runoff test, researchers compare plots with and without planted buffers at two fields. They predict that buffers remove pesticide from runoff, rather than merely reducing the amount of water leaving a plot. Lower pesticide mass with unchanged runoff volume would be particularly useful evidence for this prediction.
Runoff from paired plots
Field
Buffer?
Runoff (L)
Pesticide (mg)
A
No
10
40
A
Yes
10
20
B
No
20
60
B
Yes
10
30
Pesticide mass is the total amount measured in the collected runoff.
Which comparison most directly provides that evidence?
Why this answer
A comparison that separates competing explanations
Correct choice: At Field A, runoff was 10 liters in both plots, but pesticide mass was 20 milligrams with the buffer and 40 without.
At Field A, equal water volume accompanies lower pesticide mass with the buffer. That pattern cannot be explained merely by reducing runoff volume. Field B halves both quantities and does not separate the explanations as clearly.
A: Pesticide mass falls, but runoff volume also falls by half; this does not distinguish removal from reduced water volume.
B: This accurate comparison involves two unbuffered plots and does not evaluate buffers.
C: This establishes reduced runoff volume, the alternative the question asks you to distinguish from removal.
If you missed it: Find the comparison that holds the competing explanation's key quantity constant.
Two hypothetical cataloging teams began work at different times. The graph shows cumulative records completed since each team began, measured over the same observation weeks. A supervisor says Team S produced more records during each of the final two one-week intervals, even though S still had the lower cumulative total at week 4.
Cumulative cataloging totals
Totals include records completed before observation week 0.
Which statement best supports the supervisor's statement?
Why this answer
Cumulative totals versus recent production
Correct choice: S added 40 records in each final week versus R's 20, but finished with 100 total records versus R's 120.
From weeks 2 to 3 and 3 to 4, S adds 40 each time while R adds 20 each time. At week 4, however, S's total is 100 and R's is 120. C preserves both rate and level comparisons.
A: R's head start and higher totals are true but do not compare recent production.
B: S's two-week gain is true but does not compare teams or show each separate interval.
D: The full-period gains are accurate but do not establish the separate final-week comparisons or the remaining cumulative gap.
If you missed it: For cumulative graphs, subtract adjacent totals to find production during an interval; use endpoint heights for total production.
A hypothetical trial compared revised exhibit labels with original labels within each age and expertise group. The bars show the increase in mean recall score. A writer claims that novices benefited strictly more than experienced readers in every age group and that the novice benefit increased across the displayed age groups.
Recall improvement with revised labels
Bars show revised-label score minus original-label score within each group.
Which revision most accurately matches the data?
Why this answer
Revise an overstated claim while preserving supported parts
Correct choice: Novices gained at least as much in every group, with progressively larger novice gains across the displayed age groups.
The novice and experienced gains are equal among younger adults, 10 points each. Novice gains are larger in the middle and older groups, and novice gains increase from 10 to 20 to 30. A repairs "strictly more" while retaining the supported pattern.
B: The oldest novice gain is accurate, but it does not justify ignoring the equality among younger adults.
C: Equality in one age group does not establish equality in the other groups.
D: The experienced gain is 20 points, but the corresponding novice gain is higher, at 30.
If you missed it: For a compound claim, correct the unsupported part without discarding the part that the data support.