how to determine co-relation between two sets?

Question

Is the corelation positive, negative, Strongly positive,Strongly negative? Is there any solid quantifier by which we can differntiae betwen a strongly (+/-) and a regular +/- co-relation?
Thanks.

I am posting one table from gmatprep, what is the co-relation between the two columns viz. b/w no of lanes and avg customer age.?

lunar255 · Answer

I took this test too. The answer is "negative correlation...", but I don't understand how

Triforce · Answer

The easy way to remember is:

If, in average, x goes up/is high and y goes up/is high => positive corr
If, in average, x goes up/is high and y goes down/is low=> negative corr
and vice versa

lunar255 · Answer

I think we can explain the answer like this:

3 stores with 0 self-check lane, and the average customer ages are 50.50, 38.80, 56.70 respectively.

-> So: 0 lane - (50.50 + 38.80 + 56.70)/3 = 48.66 average age

3 stores with 4 self-check lanes, and the average customer ages are 34.50, 32.00, 42.50 respectively.

-> So: 4 lanes - (34.50 + 32.00 + 42.50)/3 = 36.33 average age

2 stores with 6 self-check lanes, and the average customer ages are 28.40 and 34.60 respectively.

-> So: 6 lanes ; (28.40 + 34.60)/2 = 31.5 average age

1 store with 8 self-check lanes, and the average customer ages is 29.90

--> negative correlation.

egmat · Answer

Well the answer is indeed negative correlation. We can follow this approach to conclude whether correlation is +/- or null. Since # of lanes is already arranged in ascending order, you may roughly draw a line graph per the Average customer age values on scratch paper as shown in the image below.

Now next step is to visualize a trend line. The given trend line descends from Top right hand quadrant to bottom left hand quadrant. This means when the values of  # of lane s are rising, the corresponding  Average customer age  values are decreasing, hence a case of negative correlation.

https://gmatclub.com/blog/wp-content/uploads/2012/12/Correlation.png

e-GMAT has launched 15+ hours of interactive audio visual content on IR. IR questions that are true reflection of Official Guide questions. It encompasses 35 concepts, 120+ original questions, and 2 full length Mock Tests.

Should you wish to see couple of questions on  correlation  with an interactive audio-visual solutions, pl. visit e-GMAT free trial.

-Best Regards!

Shalabh Jain

how to determine co-relation between two sets?

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards