GMAT Prep Question - Negative Correlation

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GMAT Prep Question - Negative Correlation

by Poisson » Mon Aug 29, 2016 2:36 pm
Hi everyone, I've tried my hand at this but I'm not understanding how question 2 can be confirmed as True. I tried plotting the points (# of self-checkout unlimited on the X-axis, average customer age on the y-axis) and I don't see any kind of correlation. Could someone please shed some light on this problem? Thanks so much
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by [email protected] » Mon Aug 29, 2016 6:09 pm
Poisson wrote:Hi everyone, I've tried my hand at this but I'm not understanding how question 2 can be confirmed as True. I tried plotting the points (# of self-checkout unlimited on the X-axis, average customer age on the y-axis) and I don't see any kind of correlation. Could someone please shed some light on this problem? Thanks so much
Think about it in terms of approximate averages:

When there are 4 lanes, the average age is: 34.5, 32, and 42, for an average of about 36.

When there are 6 lanes, the average age is 28.4 and 34.6, for an average of about 31.

When there are 8 lanes, the average age is 29.9

As the number of lanes goes up, the average age (or the average of the average age) goes down, hence the negative correlation.
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