** Insight 104; to sip or not to sip: **
This section is concerned with understanding the rum universe
in terms of rum similarity. The most direct approach to judging similarity
among types is to compare their average ratings. This is the default
approach that RumRatings
employs when ranking these spirits. Yet, while intuitive, this information
can be complemented with a secondary descriptor (pair correlation)
to gain further insights into the data.

Click for discussion on pair-correlation

**
The image below portraits an example of a rum universe with three
users, three spirits and the ratings each user has assigned to each
bottle. According to the average rating descriptor,
all three rums would be equally ranked (6 ratings on average). However,
in many cases one is interested in knowing how similar is a given
rum to another one assuming the test subject sampled both rums.
By looking at the pic is clear that the
average rating descriptor does not suffice for such purpose.
For example, the top rum and middle one are quite different
(top rum 3 ratings below middle rum) based on
the user set that tested both (only one person in this case).
Similarly, the middle rum turns out to be ((5 - 9 + 4 - 3)/2 = -1.5)
or 1.5 ratings below the bottom rum on average according to the user
group that did try both brands (two users). This one-to-one conditional
behaviour is known in mathematics
as pair correlations. **

Enter reference rum index below to build the
pair-similarity table
(Click here for rum index list).
This will create a rum list ranking bottles
starting by the most similar to the reference one. Positive
values of the rating differences imply better quality of the
listed rum with respect to the reference one. Alternatively,
negative numbers imply worst quality. Reviewer population
counts stating how many users tried both rums are also provided.

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