• 
• 16%
• Created over 29 days

We counted 3,453 reviews for this product over the span of 582 days, an average of 5.9 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 15 or fewer reviews on any given day.

However, we see the following 29 days exceeding this threshold:

• 25 Reviews on Apr 27, 2020 (Avg. rating: 4.3)
• 25 Reviews on Apr 19, 2020 (Avg. rating: 4.1)
• 24 Reviews on Apr 29, 2020 (Avg. rating: 4.3)
• 24 Reviews on Apr 26, 2020 (Avg. rating: 4.0)
• 23 Reviews on Apr 21, 2020 (Avg. rating: 4.2)
• 22 Reviews on May 10, 2020 (Avg. rating: 4.2)
• 21 Reviews on May 13, 2020 (Avg. rating: 4.4)
• 20 Reviews on Apr 23, 2020 (Avg. rating: 4.3)
• 20 Reviews on May 17, 2020 (Avg. rating: 4.2)
• 20 Reviews on May 16, 2020 (Avg. rating: 3.6)
• 19 Reviews on May 19, 2020 (Avg. rating: 4.7)
• 19 Reviews on May 6, 2020 (Avg. rating: 4.6)
• 19 Reviews on Apr 25, 2020 (Avg. rating: 4.5)
• 19 Reviews on May 14, 2020 (Avg. rating: 4.5)
• 19 Reviews on Apr 7, 2020 (Avg. rating: 4.2)
• 19 Reviews on Apr 15, 2020 (Avg. rating: 4.2)
• 19 Reviews on May 7, 2020 (Avg. rating: 4.0)
• 19 Reviews on Apr 20, 2020 (Avg. rating: 3.9)
• 18 Reviews on Apr 22, 2020 (Avg. rating: 4.3)
• 17 Reviews on Mar 7, 2020 (Avg. rating: 4.5)
• 17 Reviews on Apr 18, 2020 (Avg. rating: 4.1)
• 17 Reviews on Jan 10, 2020 (Avg. rating: 4.0)
• 17 Reviews on Dec 7, 2019 (Avg. rating: 3.8)
• 16 Reviews on May 11, 2020 (Avg. rating: 4.4)
• 16 Reviews on May 5, 2020 (Avg. rating: 4.3)
• 16 Reviews on Jan 6, 2020 (Avg. rating: 4.3)
• 16 Reviews on Apr 11, 2020 (Avg. rating: 3.9)
• 16 Reviews on Apr 13, 2020 (Avg. rating: 3.9)
• 16 Reviews on Mar 3, 2020 (Avg. rating: 3.8)
Show All

In total, we found that 558 reviews were created on just 29 days. The reviews on these high volume days have rated this product an average of 4.2 while reviews from other days have rated this product an average of 3.9. 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

• 
• 17%
• have only posted one review

570 of the 3,453 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

110 of the 3,453 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 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 Suspicious Reviewers test.

• 
• 99%
• 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:

• 0-5 words: 99.1% (Avg. rating: 4.0)

In total, we found that 3,422 reviews (or 99%) are within an overrepresented word count group. These reviews have rated this product an average of 4.0, while all other reviews have rated this product an average of 3.3. 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 Word Count Comparison test.

• 
• 8%
• Substantial overlapping review history

259 of the 3,453 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.7 while the reviewers who have a more unique product review history rated this product an average of 3.9. 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.

• 104
• Reviews have been deleted

We discovered a total of 104 deleted Reviews for this product, with an average rating of 4.8. Even though deleted reviews don't affect the average rating, the fact that action was taken to delete reviews raises some red flags about the integrity of the reviews for the product as whole.

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.

Show distribution of deleted reviews

• 
• 55%
• 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: 54.9% (Avg. rating: 3.9)

In total, we found that 1897 reviewers (or 55%) 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.

• 
• 3%
• Unverified Purchases

87 of the 3,453 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.

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

Brand Repeaters

• 
• 3%
• Reviewed other products from this brand

88 of the 3,453 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.

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.