Readability Analysis: We are interested to examine what
types of reviews affect most sales and what types of reviews
are most helpful to the users. For example, everything else
being equal, a review that is easy to read will be more helpful
than another that has spelling mistakes and is difficult to read.
As a first, low-level variable, we measured the number
of spelling mistakes within each review, and we normalized
the number by dividing with the length of the review (in
characters).3 To measure the spelling errors, we used an off the-shelf spell checker, ignoring capitalized words and words
with numbers in them. We also ignored the top-100 most
frequent non-English words that appear in the reviews: most
of them were brand names or terminology words that do not
appear in the spellcheckers list. Furthermore, to measure the
cognitive effort that a user needs in order to read a review,
we measured the length of a review in sentences, words, and
characters.
Beyond these basic features, we also used the extensive
results from research on readability. Past research has shown
that easy-reading text improves comprehension, retention, and
reading speed, and that the average reading level of the US
adult population is at the eighth grade level [47]. Therefore, a
review that can be read easily by a large number of users is also
expected to be rated by more users. Today there are numerous
metrics for measuring the readability of a text, and while none
of them is perfect, the computed measures correlate well with
the actual difficulty of reading a text. To avoid idiosyncratic
errors peculiar to a specific readability metric, we computed
a set of metrics for each review. Specifically, we computed the
following:
• Automated Readability Index
• Coleman–Liau Index
• Flesch Reading Ease
• Flesch–Kincaid Grade Level
• Gunning fog index
• SMOG
(See [48] for detailed description on how to compute each of
these metrics.) Based on research in readability, these metrics
are useful metrics for measuring how easy is for a user to
read a review.