how to determine co-relation between two sets?

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.

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 lanes are rising, the corresponding Average customer age values are decreasing, hence a case of negative correlation.



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Shalabh Jain