• 
• 4%
• Unverified Purchases

194 of the 4,776 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 3.0 while the verified purchasers have rated this product an average of 4.4. 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

• 
• 18%
• have only posted one review

880 of the 4,776 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.

Never-Verified Reviewers

• 
• 2%
• have zero verified purchases

117 of the 4,776 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 4.4. 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.

Take-Back Reviewers

• 
• 7%
• have previously deleted reviews

312 of the 4,776 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 4.6 while the reviewers who don't have any deleted reviews in their history have rated this product an average of 4.4. 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

• 
• 2%
• have posted all their reviews on a single day

81 of the 4,776 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 4.6 while all other reviewers rated this product an average of 4.4. 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.

• 
• 1%
• Substantial overlapping review history

48 of the 4,776 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 4.4. 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.

• 
• 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: 98.6% (Avg. rating: 4.4)

In total, we found that 4,707 reviews (or 99%) 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.

• 
• 47%
• 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: 47.1% (Avg. rating: 4.2)

In total, we found that 2247 reviewers (or 47%) are within an overrepresented participation group. While this is more reviews from overrepresented participation groups than we'd expect to see, these reviews do not appear to have a significant impact on the overall rating.

Read more about our Reviewer Participation test.

• 
• 4%
• Created over 26 days

We counted 4,776 reviews for this product over the span of 3,682 days, an average of 1.3 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 6 or fewer reviews on any given day.

However, we see the following 26 days exceeding this threshold:

• 15 Reviews on Feb 18, 2019 (Avg. rating: 4.6)
• 14 Reviews on Nov 1, 2017 (Avg. rating: 4.2)
• 11 Reviews on Feb 2, 2021 (Avg. rating: 4.9)
• 9 Reviews on Mar 1, 2016 (Avg. rating: 4.3)
• 9 Reviews on Jun 15, 2020 (Avg. rating: 4.3)
• 9 Reviews on May 17, 2020 (Avg. rating: 4.2)
• 8 Reviews on Mar 24, 2020 (Avg. rating: 4.8)
• 8 Reviews on Jan 4, 2019 (Avg. rating: 3.1)
• 8 Reviews on Jul 17, 2020 (Avg. rating: 3.1)
• 7 Reviews on Jun 17, 2020 (Avg. rating: 5.0)
• 7 Reviews on Jul 24, 2020 (Avg. rating: 5.0)
• 7 Reviews on Jan 25, 2021 (Avg. rating: 5.0)
• 7 Reviews on Aug 17, 2015 (Avg. rating: 4.9)
• 7 Reviews on Nov 6, 2019 (Avg. rating: 4.9)
• 7 Reviews on Sep 1, 2019 (Avg. rating: 4.7)
• 7 Reviews on Nov 18, 2019 (Avg. rating: 4.7)
• 7 Reviews on Sep 4, 2019 (Avg. rating: 4.6)
• 7 Reviews on Nov 1, 2019 (Avg. rating: 4.4)
• 7 Reviews on Dec 27, 2019 (Avg. rating: 4.4)
• 7 Reviews on Dec 8, 2019 (Avg. rating: 4.3)
• 7 Reviews on Feb 21, 2021 (Avg. rating: 4.3)
• 7 Reviews on Mar 10, 2021 (Avg. rating: 4.0)
• 7 Reviews on Jun 19, 2020 (Avg. rating: 3.9)
• 7 Reviews on Jan 27, 2019 (Avg. rating: 3.7)
• 7 Reviews on Feb 19, 2018 (Avg. rating: 2.9)
• 7 Reviews on Oct 1, 2017 (Avg. rating: 1.7)
Show All

In total, we found that 210 reviews were created on just 26 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.

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 4.3, 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.

Brand Repeaters

• 
• 2%
• Reviewed other products from this brand

108 of the 4,776 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.