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25 Mar 2026, 23:09
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I totally understand why the data might look scattered at first glance. Key Insight: negative correlation does NOT mean a perfect downward line — it just means that, overall, as one variable increases, the other tends to decrease.
Let me sort the data by self-check unlimited lanes so the pattern becomes clear:
0 unlimited lanes: Store D (50.5), Store G (38.8), Store I (56.7) — average age around 48.7
4 unlimited lanes: Store A (34.5), Store C (32.0), Store E (42.5) — average age around 36.3
6 unlimited lanes: Store B (28.4), Store F (34.6) — average age around 31.5
8 unlimited lanes: Store H (29.9) — age 29.9
Now look at the group averages as unlimited lanes increase: 48.7 → 36.3 → 31.5 → 29.9. That is a clear downward trend!
Yes, there is scatter within each group — for example, at 0 lanes, ages range from 38.8 to 56.7. But correlation measures the overall tendency, not perfection. Think of it this way: if you plotted all 9 points on a graph with unlimited lanes on the x-axis and age on the y-axis, the best-fit line would clearly slope downward. That is what makes it a negative correlation.
The GMAT trick here is that you do not need to calculate a correlation coefficient. You just need to observe: stores with MORE unlimited lanes consistently tend to have LOWER average customer ages, and stores with FEWER unlimited lanes tend to have HIGHER ages. Every single store with 6 or 8 unlimited lanes has a below-average customer age (under 38.66), while every store with 0 unlimited lanes has an above-average or near-average customer age. That overall pattern is enough to confirm a negative correlation.
Answer: True, True, False
Let me sort the data by self-check unlimited lanes so the pattern becomes clear:
0 unlimited lanes: Store D (50.5), Store G (38.8), Store I (56.7) — average age around 48.7
4 unlimited lanes: Store A (34.5), Store C (32.0), Store E (42.5) — average age around 36.3
6 unlimited lanes: Store B (28.4), Store F (34.6) — average age around 31.5
8 unlimited lanes: Store H (29.9) — age 29.9
Now look at the group averages as unlimited lanes increase: 48.7 → 36.3 → 31.5 → 29.9. That is a clear downward trend!
Yes, there is scatter within each group — for example, at 0 lanes, ages range from 38.8 to 56.7. But correlation measures the overall tendency, not perfection. Think of it this way: if you plotted all 9 points on a graph with unlimited lanes on the x-axis and age on the y-axis, the best-fit line would clearly slope downward. That is what makes it a negative correlation.
The GMAT trick here is that you do not need to calculate a correlation coefficient. You just need to observe: stores with MORE unlimited lanes consistently tend to have LOWER average customer ages, and stores with FEWER unlimited lanes tend to have HIGHER ages. Every single store with 6 or 8 unlimited lanes has a below-average customer age (under 38.66), while every store with 0 unlimited lanes has an above-average or near-average customer age. That overall pattern is enough to confirm a negative correlation.
Answer: True, True, False
03 Aug 2026, 10:56
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Second part of the question
out of 8 data points only 3 points show negative correlation this is below 50%. So how can we accurately describe it as a negative correlation. The relationship should at least be valid for 50% of the data points.
out of 8 data points only 3 points show negative correlation this is below 50%. So how can we accurately describe it as a negative correlation. The relationship should at least be valid for 50% of the data points.
05 Aug 2026, 11:06
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Hi INeel,
I can see exactly where this is coming from. Like samarpan's post above, you sorted by self-check unlimited lanes and then walked cell by cell down the age column, counting how many times age drops versus rises. You found the drops don't clear a comfortable majority, so you concluded it can't be a negative correlation.
Here's the key fix: correlation is not measured by counting consecutive point-to-point steps. Correlation asks a bigger question - as one variable goes up, does the other tend to go down overall? A single jump the "wrong" way (or several) doesn't break it, and the count of up-steps vs. down-steps isn't the test at all. In fact, since several stores are tied on unlimited lanes (three stores at 0, three at 4, two at 6), your step-by-step count even depends on the arbitrary order you list the ties in - that alone tells you it's the wrong tool.
The reliable move is to group by lane count and look at the average age in each group. Using the table's real values:
- 0 lanes (D, G, I): 50.5, 38.8, 56.7 - average ≈ 48.7
- 4 lanes (A, C, E): 34.5, 32, 42.5 - average ≈ 36.3
- 6 lanes (B, F): 28.4, 34.6 - average ≈ 31.5
- 8 lanes (H): 29.9
As lanes go 0 → 4 → 6 → 8, average age goes 48.7 → 36.3 → 31.5 → 29.9 - a clean, steady decline. That overall downward tendency is exactly what "negative correlation" means, so the answer is True.
Quick rehearsal to lock it in.
Take x = 1, 2, 3, 4 with y = 20, 22, 10, 8. Going 20 → 22 is a step up - a wrong-way move. But zoom out: high x sits with low y, low x with high y, and the best-fit line slopes clearly downward. One wrong-way step doesn't override the overall trend. Same story here - don't let a couple of exceptions outvote the big picture.
Answer: True
I can see exactly where this is coming from. Like samarpan's post above, you sorted by self-check unlimited lanes and then walked cell by cell down the age column, counting how many times age drops versus rises. You found the drops don't clear a comfortable majority, so you concluded it can't be a negative correlation.
Here's the key fix: correlation is not measured by counting consecutive point-to-point steps. Correlation asks a bigger question - as one variable goes up, does the other tend to go down overall? A single jump the "wrong" way (or several) doesn't break it, and the count of up-steps vs. down-steps isn't the test at all. In fact, since several stores are tied on unlimited lanes (three stores at 0, three at 4, two at 6), your step-by-step count even depends on the arbitrary order you list the ties in - that alone tells you it's the wrong tool.
The reliable move is to group by lane count and look at the average age in each group. Using the table's real values:
- 0 lanes (D, G, I): 50.5, 38.8, 56.7 - average ≈ 48.7
- 4 lanes (A, C, E): 34.5, 32, 42.5 - average ≈ 36.3
- 6 lanes (B, F): 28.4, 34.6 - average ≈ 31.5
- 8 lanes (H): 29.9
As lanes go 0 → 4 → 6 → 8, average age goes 48.7 → 36.3 → 31.5 → 29.9 - a clean, steady decline. That overall downward tendency is exactly what "negative correlation" means, so the answer is True.
Quick rehearsal to lock it in.
Take x = 1, 2, 3, 4 with y = 20, 22, 10, 8. Going 20 → 22 is a step up - a wrong-way move. But zoom out: high x sits with low y, low x with high y, and the best-fit line slopes clearly downward. One wrong-way step doesn't override the overall trend. Same story here - don't let a couple of exceptions outvote the big picture.
Answer: True
INeel
