Critical Reasoning

A city recently installed high-intensity LED streetlights in its commercial district to reduce night-time traffic accidents. Over the six months following the installation, the number of recorded night-time traffic accidents in the district dropped by 25 percent. City officials concluded that the improved visibility from the new LED streetlights was directly responsible for the reduction in traffic accidents. Which of the following statements, if true, most seriously weakens the city officials' conclusion?

Agricultural scientists recently developed a genetically modified variety of wheat engineered to produce a natural enzyme that repels the destructive Hessian fly. In controlled laboratory trials, crops of this modified wheat suffered 90 percent less damage from Hessian flies than conventional wheat crops did. The researchers concluded that replacing conventional wheat with this modified variety across Region X will virtually eliminate wheat crop losses caused by the Hessian fly.

Which of the following, if true, most seriously weakens the researchers' argument?

A regional supermarket chain recently installed self-checkout kiosks in half of its stores, resulting in a 15 percent decrease in average customer checkout times at those locations. Management now plans to install identical self-checkout kiosks in all of its remaining stores, concluding that this strategy will decrease average checkout times across the entire chain. Which of the following is an assumption on which the management's conclusion depends?

An organic apple orchard installed owl nesting boxes throughout its acreage six months ago to control the local field mouse population without using chemical pesticides. Recent surveys show that the field mouse population in the orchard has declined by 40 percent over the past six months. The orchard owner concludes that the presence of owls attracted by the nesting boxes caused the reduction in the field mouse population. Which of the following, if true, most seriously weakens the orchard owner's argument?

A municipal public health board recently introduced a high-dose vitamin D supplementation campaign aimed at reducing winter absenteeism among public transit workers. During the six months following the campaign's launch, sick leave days taken by transit employees declined by 22 percent compared to the same period in the previous year. Consequently, the health board concluded that the vitamin D campaign was directly responsible for the decrease in worker absenteeism. Which of the following statements, if true, most seriously weakens the public health board's argument?

Epidemiologists studying a coastal region noted a strong positive correlation over the past decade between the consumption of locally farmed shellfish and a decreased incidence of chronic systemic inflammation among residents. Reasoning that high concentrations of specific omega-3 fatty acids present in these shellfish directly suppress inflammatory pathways, local health authorities launched a public campaign encouraging all adults in the region to significantly increase their weekly shellfish intake. Which of the following statements, if true, most seriously weakens the argument for the health authorities' recommendation?

A marine conservation organization proposes installing artificial reefs along a coastal bay to boost local fish numbers. The organization reasons that because artificial reefs in neighboring bays quickly attracted large fish populations, introducing similar structures to this bay will guarantee an increase in the bay's total fish population.

Which of the following are unstated assumptions upon which the conservation organization's argument depends? Select all that apply.

To reduce the frequency and severity of wildland fires in the Sierra Nevada, forestry officials initiated a program of extensive underbrush clearing and controlled burning across public forest tracts. Researchers noted that during a subsequent five-year period of severe drought, tracts subjected to underbrush clearing experienced a 40 percent reduction in total burned acreage compared to unmanaged tracts. Consequently, officials concluded that expanding underbrush clearing to all remaining public timberlands in the region will effectively minimize large-scale forest fire damage during future drought cycles. Which of the following statements, if true, most seriously weakens the forestry officials' argument?

Archaeologists analyzing the ancient agricultural settlement of Oakhaven found that soil moisture levels dropped sharply during the eighth century CE, a period corresponding to a recorded increase in regional temperatures. Because crop yields collapsed simultaneously, the archaeologists concluded that the rise in regional temperatures was the direct cause of the soil moisture depletion and the subsequent agricultural collapse.

Which of the following, if true, most seriously weakens the archaeologists' argument?

A municipal library system plans to replace half of its physical reference desk staff with automated digital catalog kiosks, reasoning that this change will allow the library to reduce operating expenses without decreasing the total number of patrons served daily. Which of the following is an assumption upon which the library system's plan depends?

A municipal transit agency observed that after introducing free Wi-Fi service on city buses six months ago, overall passenger satisfaction ratings increased by 20 percent. The agency concluded that providing free Wi-Fi service was the primary reason for the increase in passenger satisfaction. Which of the following statements, if true, most seriously weakens the transit agency's conclusion?

To prevent paper degradation caused by seasonal humidity fluctuations, a municipal historical archive recently installed state-of-the-art automated climate-control units throughout its document vault. Based on laboratory tests showing that constant relative humidity eliminates micro-tearing in centuries-old parchment, the head archivist concluded that installing these units will significantly reduce the archive's overall expenditures on document restoration over the next five years.

Which of the following, if true, most seriously weakens the head archivist's conclusion?

To reduce the incidence of waterborne gastrointestinal infections, health authorities in Region X distributed advanced home water filtration units to households in high-risk rural villages. Over the subsequent two years, regional health clinics recorded a 25 percent increase in diagnosed cases of waterborne infections among residents of these villages. Concluding that the filtration units were ineffective at removing pathogens, health officials suspended the distribution program. Which of the following, if true, most seriously weakens the health officials' conclusion?

Recent archival analyses of nineteenth-century industrial records challenge the long-held assumption that the rapid adoption of steam-powered machinery in British textile mills was primarily driven by its immediate cost-efficiency over water power. In fact, water mills remained significantly cheaper to operate per unit of energy well into the 1840s. Rather, steam power granted mill owners unprecedented geographical flexibility, allowing them to construct factories in densely populated urban centers with vast, low-cost labor pools rather than along remote, rural rivers. Consequently, the transition to steam was fundamentally a strategy to gain leverage in labor management rather than a simple pursuit of energy economy. Therefore, historical models of industrialization must reevaluate technical innovation through the lens of labor dynamics.

Based on the argument above, which of the following statements represent main conclusions or primary claims advocated by the author? Select all that apply.

A recent survey of urban professionals found that individuals who drink green tea daily report significantly lower stress levels than those who do not drink green tea. Based on this finding, a health consultant concluded that drinking green tea directly causes a reduction in stress levels. Which of the following best describes the flaw in the health consultant's reasoning?

To address severe coastal erosion threatening its municipal beachfront, the town of Marrow Bay constructed a series of artificial offshore reefs designed to dissipate incoming wave energy. Over the two years following the installation, shoreline erosion rates along Marrow Bay decreased by 35 percent. Municipal engineers concluded that the artificial reefs were directly responsible for mitigating shoreline loss by successfully dampening wave impact forces. Which of the following, if true, most seriously weakens the municipal engineers' conclusion?

To protect native trout populations from invasive northern pike, regional conservationists installed a high-frequency acoustic barrier across the narrow inlet leading into Lake Solitude. Over the subsequent two years, monitoring surveys recorded a 40 percent decrease in the northern pike population upstream of the barrier. Concluding that the barrier successfully deterred the invasive species from migrating, officials plan to deploy similar acoustic technology across other regional waterways. Which of the following, if true, most seriously weakens the conservationists' argument?

For decades, art historians maintained that the distinctive blue glazes in early Renaissance frescoes were derived exclusively from imported lapis lazuli, a pigment so costly that its usage was strictly dictated by wealthy patrons. However, recent spectroscopic micro-analysis of plaster fragments from mid-fifteenth-century Tuscan chapels reveals widespread trace amounts of smalt, a cobalt-infused glass pigment previously thought to have been invented a century later. Although some conservators argue this discovery merely indicates later restoration efforts, the smalt particles are embedded beneath intact, original varnish layers rather than sitting atop them. Consequently, scholars must revise the long-standing timeline of inorganic pigment synthesis in Europe, recognizing that fifteenth-century artisans engaged in sophisticated chemical experimentation far earlier than historical documentation suggests.

Which of the following best expresses the main conclusion of the passage?

A city transit agency reported that bus routes equipped with free Wi-Fi received significantly higher satisfaction ratings from commuters than routes without Wi-Fi. The agency concluded that installing Wi-Fi on all remaining bus routes will directly increase satisfaction ratings across the entire transit system. Which of the following identify flaws in the reasoning above? Select all that apply.

Ecologists recently introduced a species of native predatory beetles into an agricultural valley to reduce the population of crop-damaging aphids. Over the following six months, aphid populations decreased dramatically across farms throughout the valley. The ecologists concluded that the introduction of the predatory beetles was the primary cause of the reduction in aphid populations.

Which of the following statements, if true, provide support for the ecologists' conclusion?