The ease score is the average rating for all reviews that a given reviewer submits. The average ease score for reviewers of this product is 4.9, while the average ease score for reviewers in this category is 4.2. Based on our statistical modeling, the discrepancy in average rating between these two groups is significant enough to believe that the difference is not due to random chance, and may indicate that there are unnatural reviews.

• 
• 18%
• Created over 4 days

We counted 264 reviews for this product over the span of 104 days, an average of 2.5 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 9 or fewer reviews on any given day.

However, we see the following 4 days exceeding this threshold:

• 13 Reviews on May 4, 2019 (Avg. rating: 4.9)
• 12 Reviews on May 11, 2019 (Avg. rating: 5.0)
• 11 Reviews on May 8, 2019 (Avg. rating: 5.0)
• 11 Reviews on May 9, 2019 (Avg. rating: 5.0)

In total, we found that 47 reviews were created on just 4 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

Take-Back Reviewers

• 
• 0%
• have previously deleted reviews

1 of the 264 reviewers have had at least one of their past reviews for another product deleted. While this is more Take-Back Reviewers than we'd expect to see, it does not appear to have a significant impact on the overall rating.

Read more about our Suspicious Reviewers test.

• 
• 91%
• Have an overrepresented word count

In the graph above, we can see the distribution of review word counts for this product and the expected distribution for this category. We see the following 3 groups with a statistically significant greater concentration than what we'd expect to see:

• 41-65 words: 23.5% (Avg. rating: 4.9)
• 66-100 words: 38.6% (Avg. rating: 5.0)
• 101-200 words: 29.2% (Avg. rating: 5.0)

In total, we found that 241 reviews (or 91%) are within an overrepresented word count group. This is an excessively high number of reviews in overrepresented word count groups.

Read more about our Word Count Comparison test.

• 
• 5%
• Unverified Purchases

13 of the 264 total reviews for this product are unverified purchases. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Unverified purchases may be the result of Kindle Unlimited readers, buyers who didn't pay full price, or reviewers who did not purchase the product at Amazon. Read more about our Unverified Purchases test.

• 
• 37%
• Substantial overlapping review history

97 of the 264 reviewers have substantial overlapping product review history. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Read more about our Overlapping Review History test.

• 
• 0%
• From reviewers with an overrepresented participation

We didn't find any participation groups that had a statistically significant greater concentration than what we'd expect to see in this category.
Read more about our Reviewer Participation test.

Brand Repeaters

We didn't detect a substantial amount of Brand Repeaters.

• 0
• Reviews have been deleted

We have not discovered any deleted reviews for this product.

There are a few limitations to keep in mind regarding the Deleted Reviews test:

1. We don't have a magic ability to collect every single deleted review; we can only identify reviews as deleted if we collect them on one date and then notice they are no longer visible on a subsequent date.
2. We have no information on reviews that were never published in the first place.
3. We also don't know why these reviews were removed. It could be action from the platform, personal decision by the review author, part of an entire account closure, even some data error on our part, etc.

Read more about our Deleted Reviews test.

We have not yet completed optimization for this test for Hanzi or Kanji.

We have not yet completed optimization for this test for Hanzi or Kanji.