• 
• 2%
• Unverified Purchases

110 of the 4,574 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 3.2 while the verified purchasers 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.

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.

One-Hit Wonders

• 
• 20%
• have only posted one review

929 of the 4,574 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.

Never-Verified Reviewers

• 
• 1%
• have zero verified purchases

46 of the 4,574 reviewers have never written a verified purchase review. The Never-Verified Reviewers have rated this product an average of 3.2 while the reviewers who have written at least one verified purchase review 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.

Single-Day Reviewers

• 
• 1%
• have posted all their reviews on a single day

33 of the 4,574 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 4.5 while all other reviewers 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.

• 
• 3%
• Substantial overlapping review history

137 of the 4,574 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 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 Overlapping Review History test.

• 
• 52%
• 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: 52.2% (Avg. rating: 4.0)

In total, we found that 2386 reviewers (or 52%) are within an overrepresented participation group. These reviews have rated this product an average of 4.0, while all other reviews 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 Reviewer Participation test.

• 
• 13%
• Created over 34 days

We counted 4,574 reviews for this product over the span of 950 days, an average of 4.8 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 13 or fewer reviews on any given day.

However, we see the following 34 days exceeding this threshold:

• 33 Reviews on Jul 25, 2019 (Avg. rating: 4.0)
• 28 Reviews on Jul 24, 2019 (Avg. rating: 4.2)
• 25 Reviews on Jan 15, 2020 (Avg. rating: 4.2)
• 25 Reviews on Dec 17, 2019 (Avg. rating: 3.6)
• 23 Reviews on Jan 13, 2020 (Avg. rating: 4.1)
• 22 Reviews on Apr 21, 2020 (Avg. rating: 4.5)
• 21 Reviews on May 17, 2020 (Avg. rating: 4.5)
• 20 Reviews on Jul 23, 2019 (Avg. rating: 4.4)
• 18 Reviews on Sep 17, 2020 (Avg. rating: 4.3)
• 18 Reviews on Oct 22, 2020 (Avg. rating: 4.2)
• 18 Reviews on Jan 12, 2020 (Avg. rating: 4.0)
• 17 Reviews on Jan 5, 2020 (Avg. rating: 4.4)
• 17 Reviews on Dec 18, 2019 (Avg. rating: 3.9)
• 16 Reviews on Dec 31, 2019 (Avg. rating: 4.6)
• 16 Reviews on May 10, 2020 (Avg. rating: 4.6)
• 16 Reviews on Aug 1, 2019 (Avg. rating: 4.2)
• 16 Reviews on Apr 28, 2020 (Avg. rating: 4.0)
• 16 Reviews on May 6, 2020 (Avg. rating: 3.3)
• 15 Reviews on Dec 17, 2018 (Avg. rating: 4.3)
• 15 Reviews on Dec 19, 2018 (Avg. rating: 4.3)
• 15 Reviews on Oct 21, 2020 (Avg. rating: 4.3)
• 15 Reviews on Sep 15, 2020 (Avg. rating: 4.3)
• 15 Reviews on May 3, 2020 (Avg. rating: 4.1)
• 15 Reviews on Jul 26, 2019 (Avg. rating: 3.9)
• 15 Reviews on Jul 27, 2019 (Avg. rating: 3.9)
• 15 Reviews on Oct 24, 2020 (Avg. rating: 3.6)
• 14 Reviews on Jul 24, 2020 (Avg. rating: 4.4)
• 14 Reviews on May 13, 2020 (Avg. rating: 4.1)
• 14 Reviews on May 22, 2020 (Avg. rating: 4.1)
• 14 Reviews on Jan 9, 2020 (Avg. rating: 4.1)
• 14 Reviews on Sep 25, 2020 (Avg. rating: 4.0)
• 14 Reviews on Apr 22, 2020 (Avg. rating: 3.9)
• 14 Reviews on May 14, 2020 (Avg. rating: 3.9)
• 14 Reviews on Apr 29, 2020 (Avg. rating: 3.7)
Show All

In total, we found that 597 reviews were created on just 34 days. Although any days with a larger number of reviews than expected is suspicious, the discrepancy in ratings from reviews created on these high volume days and reviews created on other days isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Rating Trend test.

• 
• 97%
• 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: 97.4% (Avg. rating: 4.0)

In total, we found that 4,454 reviews (or 97%) 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.

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

• 
• 9%
• Reviewed other products from this brand

412 of the 4,574 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.