• 
• 1%
• Unverified Purchases

2 of the 157 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 5.0. 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.

Never-Verified Reviewers

• 
• 1%
• have zero verified purchases

2 of the 157 reviewers have never written a verified purchase review. The Never-Verified Reviewers have rated this product an average of 3.0 while the reviewers who have written at least one verified purchase review rated this product an average of 5.0. 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.

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 4.9, while the average ease score for reviewers in this category is 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.

• 
• 22%
• Created over 2 days

We counted 157 reviews for this product over the span of 25 days, an average of 6.3 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 15 or fewer reviews on any given day.

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

• 17 Reviews on Dec 4, 2019 (Avg. rating: 5.0)
• 17 Reviews on Dec 6, 2019 (Avg. rating: 4.9)

In total, we found that 34 reviews were created on just 2 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

• 
• 70%
• 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 2 groups with a statistically significant greater concentration than what we'd expect to see:

• 41-65 words: 35.0% (Avg. rating: 5.0)
• 66-100 words: 35.0% (Avg. rating: 4.9)

In total, we found that 110 reviews (or 70%) 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.

• 
• 46%
• 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 6-15 Reviews: 45.9% (Avg. rating: 5.0)

In total, we found that 72 reviewers (or 46%) are within an overrepresented participation group. While this is more reviews from overrepresented participation groups than we'd expect to see, the discrepancy in ratings between reviewers in an overrepresented participation groups and all other reviewers isn’t significant enough to rule out the possibility of it being due to random chance.

Read more about our Reviewer Participation test.

• 
• 22%
• Substantial overlapping review history

34 of the 157 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

We didn't detect a substantial amount of Brand Repeaters.

• 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.