• 
• 11%
• Created over 15 days

We counted 1,404 reviews for this product over the span of 1,452 days, an average of 1.0 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 5 or fewer reviews on any given day.

However, we see the following 15 days exceeding this threshold:

• 21 Reviews on Sep 5, 2015 (Avg. rating: 4.6)
• 18 Reviews on Sep 12, 2015 (Avg. rating: 4.7)
• 15 Reviews on Sep 4, 2015 (Avg. rating: 4.6)
• 12 Reviews on Sep 13, 2015 (Avg. rating: 4.6)
• 11 Reviews on Sep 7, 2015 (Avg. rating: 4.5)
• 10 Reviews on Sep 6, 2015 (Avg. rating: 4.5)
• 9 Reviews on Sep 11, 2015 (Avg. rating: 4.8)
• 9 Reviews on Sep 14, 2015 (Avg. rating: 4.8)
• 8 Reviews on Sep 9, 2015 (Avg. rating: 4.5)
• 6 Reviews on Oct 5, 2016 (Avg. rating: 4.7)
• 6 Reviews on Sep 20, 2015 (Avg. rating: 4.5)
• 6 Reviews on Nov 23, 2015 (Avg. rating: 4.5)
• 6 Reviews on Nov 20, 2015 (Avg. rating: 4.2)
• 6 Reviews on Sep 27, 2015 (Avg. rating: 4.0)
• 6 Reviews on Oct 8, 2016 (Avg. rating: 4.0)
Show All

In total, we found that 149 reviews were created on just 15 days. The reviews on these high volume days have rated this product an average of 4.5 while reviews from other days have rated this product an average of 4.0. 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.

Read more about our Rating Trend test.

One-Hit Wonders

• 
• 4%
• have only posted one review

51 of the 1,404 reviewers have only reviewed this product. The One-Hit Wonders have rated this product an average of 3.3 while the reviewers who have posted more than one review have rated this product an average of 4.1. 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.

Take-Back Reviewers

• 
• 2%
• have previously deleted reviews

28 of the 1,404 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, the discrepancy in ratings between the Take-Back Reviewers and reviewers who don't have any deleted reviews in their history isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Suspicious Reviewers test.

• 
• 14%
• Substantial overlapping review history

192 of the 1,404 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.5 while the reviewers who have a more unique product review history rated this product an average of 4.0. 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.

Read more about our Overlapping Review History test.

• 
• 71%
• 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:

• 16-25 words: 25.5% (Avg. rating: 4.2)
• 26-40 words: 22.9% (Avg. rating: 4.1)
• 41-65 words: 22.9% (Avg. rating: 4.0)

In total, we found that 1,002 reviews (or 71%) 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.

• 
• 4%
• Unverified Purchases

55 of the 1,404 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.

• 
• 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.

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 4.1, while the average ease score for reviewers in this category is 4.2.

Brand Repeaters

• 
• 3%
• Reviewed other products from this brand

46 of the 1,404 reviewers have reviewed other products for this brand. 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 Brand Repeats test.

• 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.