• 
• 16%
• Created over 11 days

We counted 451 reviews for this product over the span of 1,515 days, an average of 0.3 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 3 or fewer reviews on any given day.

However, we see the following 11 days exceeding this threshold:

• 13 Reviews on Aug 8, 2015 (Avg. rating: 4.2)
• 11 Reviews on Aug 7, 2015 (Avg. rating: 4.9)
• 10 Reviews on Aug 9, 2015 (Avg. rating: 3.9)
• 7 Reviews on Aug 13, 2015 (Avg. rating: 3.6)
• 5 Reviews on Aug 12, 2015 (Avg. rating: 4.2)
• 5 Reviews on Aug 19, 2015 (Avg. rating: 3.8)
• 5 Reviews on Feb 27, 2018 (Avg. rating: 3.8)
• 5 Reviews on Sep 11, 2015 (Avg. rating: 3.4)
• 4 Reviews on Sep 7, 2015 (Avg. rating: 3.5)
• 4 Reviews on Aug 14, 2015 (Avg. rating: 3.3)
• 4 Reviews on Aug 24, 2015 (Avg. rating: 2.8)
Show All

In total, we found that 73 reviews were created on just 11 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

• 
• 47%
• 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: 47.5% (Avg. rating: 4.0)

In total, we found that 214 reviewers (or 47%) are within an overrepresented participation group. While this is more reviews from overrepresented participation groups than we'd expect to see, these reviews do not appear to have a significant impact on the overall rating.

Read more about our Reviewer Participation test.

• 
• 16%
• Unverified Purchases

71 of the 451 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%
• 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.

One-Hit Wonders

• 
• 8%
• have only posted one review

36 of the 451 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

• 
• 11%
• have zero verified purchases

49 of the 451 reviewers have never written a verified purchase review. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Take-Back Reviewers

• 
• 2%
• have previously deleted reviews

10 of the 451 reviewers have had at least one of their past reviews for another product deleted. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Single-Day Reviewers

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

10 of the 451 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.

• 
• 9%
• Substantial overlapping review history

39 of the 451 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 4.1, while the average ease score for reviewers in this category is 4.2.

Brand Repeaters

• 
• 0%
• Reviewed other products from this brand

1 of the 451 reviewers have reviewed other products for this brand. 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 Brand Repeats test.

• 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.