One-Hit Wonders

• 
• 27%
• have only posted one review

409 of the 1,505 reviewers have only reviewed this product. While this is more One-Hit Wonders than we'd expect to see, the discrepancy in ratings between the One-Hit Wonders and reviewers who have posted more than one review isn't significant enough to rule out the possibility of it being due to random chance.

Single-Day Reviewers

• 
• 0%
• have posted all their reviews on a single day

4 of the 1,505 reviewers have written multiple reviews but posted all of them on a single day. The Single-Day reviewers have rated this product an average of 3.3 while all other reviewers rated this product an average of 4.5. 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 Suspicious Reviewers test.

• 4
• Reviews have been deleted

We discovered a total of 4 deleted Reviews for this product, with an average rating of 4.5. 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

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 4.4, while the average ease score for reviewers in this category is 4.2. While this discrepancy is rather large, it is not quite large enough to rule out the possibility of it being due random chance.

• 
• 59%
• 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:

• 41-65 words: 22.9% (Avg. rating: 4.5)
• 66-100 words: 17.9% (Avg. rating: 4.6)
• 101-200 words: 18.5% (Avg. rating: 4.4)

In total, we found that 892 reviews (or 59%) 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.

• 
• 65%
• 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: 65.1% (Avg. rating: 4.5)

In total, we found that 979 reviewers (or 65%) 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%
• Created over 5 days

We counted 1,505 reviews for this product over the span of 690 days, an average of 2.2 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 8 or fewer reviews on any given day.

However, we see the following 5 days exceeding this threshold:

• 12 Reviews on Jan 18, 2019 (Avg. rating: 4.5)
• 9 Reviews on Apr 27, 2018 (Avg. rating: 4.8)
• 9 Reviews on Aug 14, 2018 (Avg. rating: 4.6)
• 9 Reviews on Jan 12, 2019 (Avg. rating: 4.6)
• 9 Reviews on May 2, 2018 (Avg. rating: 4.4)

In total, we found that 48 reviews were created on just 5 days. 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 Rating Trend test.

• 
• 10%
• Unverified Purchases

143 of the 1,505 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%
• Substantial overlapping review history

0 of the 1,505 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.

Brand Repeaters

• 
• 1%
• Reviewed other products from this brand

18 of the 1,505 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.