• 
• 7%
• Unverified Purchases

171 of the 2,600 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 4.7 while the verified purchasers have rated this product an average of 4.6. 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.

One-Hit Wonders

• 
• 60%
• have only posted one review

1,556 of the 2,600 reviewers have only reviewed this product. This is an excessively large percentage of One-Hit Wonders which may indicate unnatural reviews.

Never-Verified Reviewers

• 
• 5%
• have zero verified purchases

137 of the 2,600 reviewers have never written a verified purchase review. The Never-Verified Reviewers have rated this product an average of 4.7 while the reviewers who have written at least one verified purchase review rated this product an average of 4.6. 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 4.5, 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.

• 
• 89%
• 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: 89.3% (Avg. rating: 4.6)

In total, we found that 2321 reviewers (or 89%) are within an overrepresented participation group. These reviews have rated this product an average of 4.6, while all other reviews 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.

Read more about our Reviewer Participation test.

• 114
• Reviews have been deleted

We discovered a total of 114 deleted Reviews for this product, with an average rating of 4.8. Even though deleted reviews don't affect the average rating, the fact that action was taken to delete reviews raises some red flags about the integrity of the reviews for the product as whole.

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.

Show distribution of deleted reviews

• 
• 20%
• Created over 18 days

We counted 2,600 reviews for this product over the span of 250 days, an average of 10.4 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 22 or fewer reviews on any given day.

However, we see the following 18 days exceeding this threshold:

• 53 Reviews on Jul 19, 2019 (Avg. rating: 4.6)
• 45 Reviews on Jul 21, 2019 (Avg. rating: 4.6)
• 39 Reviews on Jul 20, 2019 (Avg. rating: 4.4)
• 34 Reviews on Jul 18, 2019 (Avg. rating: 4.6)
• 28 Reviews on Mar 30, 2019 (Avg. rating: 4.8)
• 28 Reviews on Jun 29, 2019 (Avg. rating: 4.4)
• 27 Reviews on Mar 31, 2019 (Avg. rating: 4.7)
• 26 Reviews on May 14, 2019 (Avg. rating: 4.9)
• 26 Reviews on Jul 7, 2019 (Avg. rating: 4.7)
• 26 Reviews on May 13, 2019 (Avg. rating: 4.5)
• 25 Reviews on Jul 6, 2019 (Avg. rating: 4.6)
• 25 Reviews on Jul 23, 2019 (Avg. rating: 4.1)
• 24 Reviews on Jun 30, 2019 (Avg. rating: 4.7)
• 24 Reviews on Apr 1, 2019 (Avg. rating: 4.7)
• 24 Reviews on Jul 17, 2019 (Avg. rating: 4.6)
• 24 Reviews on Apr 2, 2019 (Avg. rating: 4.6)
• 24 Reviews on Jul 22, 2019 (Avg. rating: 4.4)
• 23 Reviews on Jul 5, 2019 (Avg. rating: 4.7)
Show All

In total, we found that 525 reviews were created on just 18 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

• 
• 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:

• 41-65 words: 30.8% (Avg. rating: 4.6)
• 66-100 words: 20.4% (Avg. rating: 4.6)

In total, we found that 1,329 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.

• 
• 0%
• Substantial overlapping review history

0 of the 2,600 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.

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.