• 
• 26%
• Created over 50 days

We counted 1,970 reviews for this product over the span of 1,254 days, an average of 1.6 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 7 or fewer reviews on any given day.

However, we see the following 50 days exceeding this threshold:

• 17 Reviews on Feb 18, 2018 (Avg. rating: 4.9)
• 17 Reviews on Feb 16, 2018 (Avg. rating: 4.4)
• 14 Reviews on Feb 15, 2018 (Avg. rating: 4.7)
• 13 Reviews on Aug 23, 2018 (Avg. rating: 4.2)
• 13 Reviews on Sep 5, 2018 (Avg. rating: 4.1)
• 13 Reviews on Sep 26, 2018 (Avg. rating: 3.9)
• 13 Reviews on Oct 13, 2018 (Avg. rating: 3.8)
• 13 Reviews on Aug 24, 2018 (Avg. rating: 3.8)
• 13 Reviews on Oct 8, 2018 (Avg. rating: 3.7)
• 12 Reviews on Sep 27, 2018 (Avg. rating: 4.8)
• 12 Reviews on Oct 4, 2018 (Avg. rating: 4.2)
• 12 Reviews on Oct 16, 2018 (Avg. rating: 3.8)
• 12 Reviews on Sep 11, 2018 (Avg. rating: 3.7)
• 11 Reviews on Sep 19, 2018 (Avg. rating: 4.1)
• 11 Reviews on Aug 30, 2018 (Avg. rating: 4.0)
• 11 Reviews on Jul 25, 2018 (Avg. rating: 3.9)
• 11 Reviews on Sep 24, 2018 (Avg. rating: 3.5)
• 10 Reviews on Oct 6, 2018 (Avg. rating: 4.5)
• 10 Reviews on Aug 31, 2018 (Avg. rating: 4.4)
• 10 Reviews on Aug 27, 2018 (Avg. rating: 4.3)
• 10 Reviews on Sep 15, 2018 (Avg. rating: 4.2)
• 10 Reviews on Sep 25, 2018 (Avg. rating: 4.0)
• 10 Reviews on Oct 17, 2018 (Avg. rating: 3.9)
• 10 Reviews on Jul 2, 2018 (Avg. rating: 3.9)
• 10 Reviews on Sep 18, 2018 (Avg. rating: 3.9)
• 10 Reviews on Sep 17, 2018 (Avg. rating: 3.7)
• 10 Reviews on Sep 13, 2018 (Avg. rating: 3.5)
• 10 Reviews on Oct 15, 2018 (Avg. rating: 3.1)
• 10 Reviews on Oct 10, 2018 (Avg. rating: 2.8)
• 9 Reviews on Feb 13, 2018 (Avg. rating: 4.9)
• 9 Reviews on Nov 4, 2018 (Avg. rating: 4.1)
• 9 Reviews on Jun 10, 2018 (Avg. rating: 4.1)
• 9 Reviews on Oct 11, 2018 (Avg. rating: 4.0)
• 9 Reviews on Oct 1, 2018 (Avg. rating: 3.9)
• 9 Reviews on Sep 10, 2018 (Avg. rating: 3.7)
• 9 Reviews on May 31, 2018 (Avg. rating: 3.7)
• 9 Reviews on Oct 3, 2018 (Avg. rating: 3.4)
• 9 Reviews on Aug 7, 2018 (Avg. rating: 3.4)
• 9 Reviews on Sep 9, 2018 (Avg. rating: 3.3)
• 9 Reviews on Sep 4, 2018 (Avg. rating: 3.3)
• 9 Reviews on Oct 28, 2018 (Avg. rating: 3.1)
• 8 Reviews on Jul 29, 2018 (Avg. rating: 4.9)
• 8 Reviews on Feb 17, 2018 (Avg. rating: 4.8)
• 8 Reviews on Jul 21, 2018 (Avg. rating: 4.5)
• 8 Reviews on Feb 14, 2018 (Avg. rating: 4.5)
• 8 Reviews on Oct 19, 2018 (Avg. rating: 4.5)
• 8 Reviews on Sep 20, 2018 (Avg. rating: 4.0)
• 8 Reviews on Sep 12, 2018 (Avg. rating: 3.9)
• 8 Reviews on Sep 8, 2018 (Avg. rating: 3.8)
• 8 Reviews on Jun 4, 2018 (Avg. rating: 3.3)
Show All

In total, we found that 518 reviews were created on just 50 days. The reviews on these high volume days have rated this product an average of 4.0 while reviews from other days have rated this product an average of 3.8. 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

• 
• 23%
• have only posted one review

444 of the 1,970 reviewers have only reviewed this product. While this is more One-Hit Wonders than we'd expect to see, it does not appear to have a significant impact on the overall rating.

Take-Back Reviewers

• 
• 3%
• have previously deleted reviews

61 of the 1,970 reviewers have had at least one of their past reviews for another product deleted. The Take-Back Reviewers have rated this product an average of 4.2 while the reviewers who don't have any deleted reviews in their history have rated this product an average of 3.8. 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 Suspicious Reviewers test.

• 
• 5%
• Substantial overlapping review history

108 of the 1,970 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.2 while the reviewers who have a more unique product review history rated this product an average of 3.8. 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.

• 
• 62%
• From reviewers with an overrepresented participation

We see the following 1 participation group with a statistically significant greater concentration than what we'd expect to see:

• Reviewers with 1-5 Reviews: 61.7% (Avg. rating: 3.8)

In total, we found that 1216 reviewers (or 62%) are within an overrepresented participation group. This is an excessively high number of reviewers in overrepresented participation groups.

Read more about our Reviewer Participation test.

• 
• 16%
• Unverified Purchases

313 of the 1,970 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.

• 
• 18%
• 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 1 group with a statistically significant greater concentration than what we'd expect to see:

• 101-200 words: 18.1% (Avg. rating: 3.8)

In total, we found that 357 reviews (or 18%) are within an overrepresented word count group. 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 Word Count Comparison 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 3.9, while the average ease score for reviewers in this category is 4.2.

Brand Repeaters

• 
• 5%
• Reviewed other products from this brand

99 of the 1,970 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.