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 4.8, 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.

• 
• 19%
• Created over 4 days

We counted 79 reviews for this product over the span of 3,618 days, an average of 0.0 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 1 or fewer reviews on any given day.

However, we see the following 4 days exceeding this threshold:

• 6 Reviews on Dec 25, 2018 (Avg. rating: 5.0)
• 4 Reviews on Dec 26, 2018 (Avg. rating: 5.0)
• 3 Reviews on Apr 20, 2019 (Avg. rating: 5.0)
• 2 Reviews on Dec 22, 2018 (Avg. rating: 5.0)

In total, we found that 15 reviews were created on just 4 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

• 
• 53%
• Unverified Purchases

42 of the 79 total reviews for this product are unverified purchases. While this is a higher percentage of unverified purchases than we'd expect to see, the discrepancy in ratings between the unverified purchases and verified purchases isn't significant enough to rule out the possibility of it being due to random chance.

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

• 
• 38%
• have zero verified purchases

30 of the 79 reviewers have never written a verified purchase review. While this is more Never-Verified Reviewers than we'd expect to see, the discrepancy in ratings between the Never-Verified Reviewers and reviewers who have written at least one verified purchase review isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Suspicious Reviewers test.

• 
• 38%
• 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: 38.0% (Avg. rating: 5.0)

In total, we found that 30 reviewers (or 38%) 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.

• 
• 0%
• Have an overrepresented word count

We didn't find any review word count groups that had a statistically significant greater concentration than what we'd expect to see in this category.
Read more about our Word Count Comparison test.

• 
• 30%
• Substantial overlapping review history

24 of the 79 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.