• 
• 1%
• Unverified Purchases

3 of the 215 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 2.0 while the verified purchasers 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.

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.

• 
• 82%
• Substantial overlapping review history

177 of the 215 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.4 while the reviewers who have a more unique product review history rated this product an average of 4.1. 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.

• 
• 67%
• 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 51-100 Reviews: 35.8% (Avg. rating: 4.3)
• Reviewers with 101-200 Reviews: 31.6% (Avg. rating: 4.4)

In total, we found that 145 reviewers (or 67%) are within an overrepresented participation group. These reviews have rated this product an average of 4.4, while all other reviews have rated this product an average of 4.2. 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.

• 
• 64%
• Created over 15 days

We counted 215 reviews for this product over the span of 430 days, an average of 0.5 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 15 days exceeding this threshold:

• 16 Reviews on Apr 1, 2019 (Avg. rating: 4.4)
• 15 Reviews on Apr 2, 2019 (Avg. rating: 4.3)
• 14 Reviews on Mar 25, 2019 (Avg. rating: 4.5)
• 13 Reviews on Mar 31, 2019 (Avg. rating: 4.4)
• 12 Reviews on Mar 28, 2019 (Avg. rating: 4.3)
• 10 Reviews on Mar 24, 2019 (Avg. rating: 4.1)
• 9 Reviews on Mar 23, 2019 (Avg. rating: 4.7)
• 8 Reviews on Apr 3, 2019 (Avg. rating: 4.3)
• 7 Reviews on Apr 8, 2019 (Avg. rating: 4.4)
• 7 Reviews on Mar 26, 2019 (Avg. rating: 3.9)
• 6 Reviews on Apr 5, 2019 (Avg. rating: 4.5)
• 6 Reviews on Apr 7, 2019 (Avg. rating: 3.5)
• 5 Reviews on Mar 29, 2019 (Avg. rating: 4.2)
• 5 Reviews on Mar 30, 2019 (Avg. rating: 4.2)
• 5 Reviews on Apr 6, 2019 (Avg. rating: 4.2)
Show All

In total, we found that 138 reviews were created on just 15 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

Take-Back Reviewers

• 
• 49%
• have previously deleted reviews

106 of the 215 reviewers have had at least one of their past reviews for another product deleted. While this is more Take-Back Reviewers than we'd expect to see, the discrepancy in ratings between the Take-Back Reviewers and reviewers who don't have any deleted reviews in their history isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Suspicious Reviewers 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: 4.3)

In total, we found that 212 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.

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

• 
• 4%
• Reviewed other products from this brand

8 of the 215 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.