• 
• 36%
• 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: 36.2% (Avg. rating: 4.9)

In total, we found that 25 reviewers (or 36%) are within an overrepresented participation group. These reviews have rated this product an average of 4.9, while all other reviews have rated this product an average of 4.5. 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.

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 4.4, 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.

• 
• 51%
• 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:

• 26-40 words: 27.5% (Avg. rating: 4.7)
• 66-100 words: 23.2% (Avg. rating: 4.7)

In total, we found that 35 reviews (or 51%) 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.

• 
• 3%
• Created over 1 day

We counted 69 reviews for this product over the span of 2,556 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 1 day exceeding this threshold:

• 2 Reviews on May 4, 2016 (Avg. rating: 4.5)

In total, we found that 2 reviews were created on just 1 day. 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.

• 
• 1%
• Unverified Purchases

1 of the 69 total reviews for this product are unverified purchases. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

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

• 
• 6%
• have only posted one review

4 of the 69 reviewers have only reviewed this product. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Never-Verified Reviewers

We didn't detect a substantial amount of Never-Verified Reviewers.

Take-Back Reviewers

We didn't detect a substantial amount of Take-Back Reviewers.

Single-Day Reviewers

• 
• 3%
• have posted all their reviews on a single day

2 of the 69 reviewers have written multiple reviews but posted all of them on a single day. 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 Suspicious Reviewers test.

• 
• 6%
• Substantial overlapping review history

4 of the 69 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.