• 
• 4%
• Unverified Purchases

6 of the 147 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 3.7 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.

• 
• 7%
• Created over 2 days

We counted 147 reviews for this product over the span of 1,288 days, an average of 0.1 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 2 or fewer reviews on any given day.

However, we see the following 2 days exceeding this threshold:

• 8 Reviews on Nov 1, 2017 (Avg. rating: 4.3)
• 3 Reviews on Nov 15, 2017 (Avg. rating: 4.7)

In total, we found that 11 reviews were created on just 2 days. Although any days with a larger number of reviews than expected is suspicious, these reviews do not appear to have a significant impact on the overall rating.

Read more about our Rating Trend test.

Brand Repeaters

• 
• 28%
• Reviewed other products from this brand

41 of the 147 reviewers have reviewed other products for this brand. While this is more Brand Repeaters than we'd expect to see, it does not appear to have a significant impact on the overall rating.

Read more about our Brand Repeats test.

Take-Back Reviewers

• 
• 36%
• have previously deleted reviews

53 of the 147 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: 99.3% (Avg. rating: 4.4)

In total, we found that 146 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.

• 
• 31%
• Substantial overlapping review history

46 of the 147 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.

• 
• 16%
• 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 101-200 Reviews: 15.7% (Avg. rating: 4.5)

In total, we found that 23 reviewers (or 16%) are within an overrepresented participation group. 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 Reviewer Participation 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.

• 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.