• 
• 11%
• Created over 8 days

We counted 590 reviews for this product over the span of 974 days, an average of 0.6 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 4 or fewer reviews on any given day.

However, we see the following 8 days exceeding this threshold:

• 17 Reviews on Mar 11, 2019 (Avg. rating: 5.0)
• 13 Reviews on Mar 19, 2019 (Avg. rating: 5.0)
• 7 Reviews on Sep 23, 2019 (Avg. rating: 4.6)
• 5 Reviews on Apr 27, 2017 (Avg. rating: 5.0)
• 5 Reviews on Apr 25, 2017 (Avg. rating: 4.4)
• 5 Reviews on Sep 26, 2017 (Avg. rating: 4.4)
• 5 Reviews on May 28, 2017 (Avg. rating: 4.2)
• 5 Reviews on Jun 24, 2019 (Avg. rating: 4.2)
Show All

In total, we found that 62 reviews were created on just 8 days. The reviews on these high volume days have rated this product an average of 4.7 while reviews from other days have rated this product an average of 4.3. 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 Rating Trend test.

• 11
• Reviews have been deleted

We discovered a total of 11 deleted Reviews for this product, with an average rating of 5. 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

One-Hit Wonders

• 
• 16%
• have only posted one review

92 of the 590 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.

Read more about our Suspicious Reviewers test.

• 
• 78%
• From reviewers with an overrepresented participation

We see the following 2 participation groups with a statistically significant greater concentration than what we'd expect to see:

• Reviewers with 1-5 Reviews: 44.2% (Avg. rating: 4.3)
• Reviewers with 6-15 Reviews: 33.9% (Avg. rating: 4.3)

In total, we found that 461 reviewers (or 78%) 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

16 of the 590 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%
• Have an overrepresented word count

We didn't find any review word count groups that had a statistically significant greater concentration than what we'd expect to see in this category.
Read more about our Word Count Comparison test.

• 
• 4%
• Substantial overlapping review history

24 of the 590 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.

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

Brand Repeaters

• 
• 4%
• Reviewed other products from this brand

23 of the 590 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.