• 
• 11%
• Created over 32 days

We counted 4,778 reviews for this product over the span of 1,122 days, an average of 4.3 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 13 or fewer reviews on any given day.

However, we see the following 32 days exceeding this threshold:

• 29 Reviews on Aug 4, 2017 (Avg. rating: 4.1)
• 23 Reviews on Jul 9, 2017 (Avg. rating: 4.4)
• 20 Reviews on Aug 1, 2017 (Avg. rating: 4.2)
• 20 Reviews on Aug 20, 2017 (Avg. rating: 4.2)
• 20 Reviews on Aug 22, 2017 (Avg. rating: 4.0)
• 18 Reviews on Jul 4, 2017 (Avg. rating: 4.5)
• 18 Reviews on Aug 21, 2017 (Avg. rating: 4.3)
• 18 Reviews on Jul 31, 2017 (Avg. rating: 4.1)
• 17 Reviews on Jul 20, 2017 (Avg. rating: 4.6)
• 17 Reviews on Jun 30, 2017 (Avg. rating: 4.5)
• 17 Reviews on Jul 13, 2017 (Avg. rating: 4.4)
• 17 Reviews on Jul 11, 2017 (Avg. rating: 4.2)
• 17 Reviews on Sep 8, 2017 (Avg. rating: 4.2)
• 17 Reviews on Sep 27, 2017 (Avg. rating: 4.2)
• 17 Reviews on Aug 28, 2017 (Avg. rating: 3.3)
• 16 Reviews on Jul 7, 2017 (Avg. rating: 4.7)
• 16 Reviews on Jul 5, 2017 (Avg. rating: 4.6)
• 16 Reviews on Jul 10, 2017 (Avg. rating: 4.4)
• 16 Reviews on Oct 4, 2017 (Avg. rating: 3.9)
• 16 Reviews on Jul 12, 2017 (Avg. rating: 3.8)
• 15 Reviews on Aug 2, 2017 (Avg. rating: 4.5)
• 15 Reviews on Jul 17, 2017 (Avg. rating: 4.1)
• 15 Reviews on Aug 5, 2017 (Avg. rating: 4.1)
• 15 Reviews on Sep 9, 2017 (Avg. rating: 3.7)
• 14 Reviews on Jul 24, 2017 (Avg. rating: 4.4)
• 14 Reviews on Jul 23, 2017 (Avg. rating: 4.3)
• 14 Reviews on Jul 6, 2017 (Avg. rating: 4.3)
• 14 Reviews on Jul 15, 2017 (Avg. rating: 4.1)
• 14 Reviews on Jan 4, 2018 (Avg. rating: 4.1)
• 14 Reviews on Sep 5, 2017 (Avg. rating: 4.1)
• 14 Reviews on Jul 30, 2017 (Avg. rating: 3.7)
• 14 Reviews on Aug 29, 2017 (Avg. rating: 3.1)
Show All

In total, we found that 537 reviews were created on just 32 days. The reviews on these high volume days have rated this product an average of 4.2 while reviews from other days have rated this product an average of 3.6. 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 Rating Trend test.

One-Hit Wonders

• 
• 23%
• have only posted one review

1,121 of the 4,778 reviewers have only reviewed this product. The One-Hit Wonders have rated this product an average of 3.8 while the reviewers who have posted more than one review have rated this product an average of 3.6. 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.

Single-Day Reviewers

• 
• 2%
• have posted all their reviews on a single day

95 of the 4,778 reviewers have written multiple reviews but posted all of them on a single day. The Single-Day reviewers have rated this product an average of 4.0 while all other reviewers rated this product an average of 3.6. 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.

• 
• 100%
• 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: 99.9% (Avg. rating: 3.6)

In total, we found that 4,772 reviews (or 100%) are within an overrepresented word count group. These reviews have rated this product an average of 3.6, while all other reviews have rated this product an average of 2.3. 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 Word Count Comparison test.

• 
• 60%
• 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: 60.3% (Avg. rating: 3.7)

In total, we found that 2882 reviewers (or 60%) are within an overrepresented participation group. These reviews have rated this product an average of 3.7, while all other reviews have rated this product an average of 3.6. 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 Reviewer Participation test.

Brand Loyalists

• 
• 3%
• Reviewed mostly products from this brand

160 of the 4,778 reviewers have reviewed multiple products but half or more of their reviews are for this brand. While this is more Brand Loyalists than we'd expect to see, the discrepancy in ratings between the Brand Loyalists and non-loyalists isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Brand Repeats test.

• 
• 5%
• Unverified Purchases

258 of the 4,778 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.

• 
• 0%
• Substantial overlapping review history

0 of the 4,778 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.

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 3.8, while the average ease score for reviewers in this category is 4.2.

• 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.