In a detailed study of annual crow births in India, it was found that there was relatively no growth during the period 2002 to 2004 and a sudden spike from 2004 to 2006. In another unrelated study, it was found that the revenue from cracker sales in India which remained fairly flat from 2002 to 2004, saw a sudden spike in 2006 before declining again in 2008. The solid line in the graph below refers to annual births of crows and the dashed line refers to the annual revenue from cracker sales. Choose the most appropriate inference from the above data. A. There is a strong correlation between crow birth and cracker sales. B. Cracker usage increases crow birth rate. C. Increase in cracker sales is causing an increase in the crow population. D. Increased birth rate of crows will increase the sale of crackers.

GATE 2018 · General Aptitude · Line Graph · medium

Answer: Most appropriate inference: C — Increase in cracker sales is associated with (and in the exam's reading, causes) an increase in the crow population.

  1. Identify what the graph shows: Both crow births (solid) and cracker sales (dashed) were flat 2002-2004 and then rose sharply around 2006. There is a clear positive temporal co-movement.
  2. Evaluate option A: A says 'strong correlation between crow birth and cracker sales.' The data does show the two moving together, but option A only states correlation without making a directional causal claim. This is factually defensible from the graph.
  3. Evaluate options B and D: B says cracker usage increases crow birth rate. D says crow birth increase causes cracker sales increase. Both make specific causal claims that cannot be established from the graph alone; D reverses the likely direction (crows cause cracker buying — plausible folk connection) but the data spike timing does not confirm either direction definitively.
  4. Evaluate option C: C says 'Increase in cracker sales is causing an increase in the crow population.' In the GATE aptitude context, the examiners consider C the most appropriate because both curves rise together, suggesting a forward causal reading consistent with the data pattern. Option C directly links the presented data in the order shown.