• 
• 14%
• Created over 4 days

We counted 171 reviews for this product over the span of 426 days, an average of 0.4 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 4 days exceeding this threshold:

• 7 Reviews on Mar 31, 2019 (Avg. rating: 4.9)
• 7 Reviews on Mar 27, 2019 (Avg. rating: 4.1)
• 5 Reviews on Mar 24, 2019 (Avg. rating: 4.6)
• 5 Reviews on Mar 28, 2019 (Avg. rating: 4.6)

In total, we found that 24 reviews were created on just 4 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 3.6. 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.

Brand Loyalists

• 
• 4%
• Reviewed mostly products from this brand

7 of the 171 reviewers have reviewed multiple products but half or more of their reviews are for this brand. This is an excessively large percentage of Brand Loyalists which may indicate unnatural reviews.

Read more about our Brand Repeats test.

• 
• 21%
• Substantial overlapping review history

36 of the 171 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.6 while the reviewers who have a more unique product review history rated this product an average of 3.5. 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.

• 2
• Reviews have been deleted

We discovered a total of 2 deleted Reviews for this product, with an average rating of 4. 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

• 
• 14%
• have only posted one review

24 of the 171 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.

• 
• 96%
• 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: 96.5% (Avg. rating: 3.8)

In total, we found that 165 reviews (or 96%) 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.

• 
• 91%
• 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: 54.4% (Avg. rating: 3.6)
• Reviewers with 6-15 Reviews: 36.8% (Avg. rating: 4.0)

In total, we found that 156 reviewers (or 91%) 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.

• 
• 18%
• Unverified Purchases

31 of the 171 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 3.9, while the average ease score for reviewers in this category is 4.2.

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.