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.

• 
• 6%
• Created over 15 days

We counted 1,255 reviews for this product over the span of 5,058 days, an average of 0.2 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 15 days exceeding this threshold:

• 10 Reviews on Jan 17, 2019 (Avg. rating: 5.0)
• 6 Reviews on Feb 18, 2019 (Avg. rating: 5.0)
• 5 Reviews on Dec 22, 2018 (Avg. rating: 4.8)
• 5 Reviews on Jan 20, 2019 (Avg. rating: 4.8)
• 4 Reviews on Jun 7, 2016 (Avg. rating: 5.0)
• 4 Reviews on Sep 2, 2017 (Avg. rating: 5.0)
• 4 Reviews on Dec 24, 2018 (Avg. rating: 5.0)
• 4 Reviews on Jan 18, 2019 (Avg. rating: 5.0)
• 4 Reviews on Feb 3, 2019 (Avg. rating: 5.0)
• 4 Reviews on Dec 26, 2018 (Avg. rating: 4.8)
• 4 Reviews on Feb 9, 2013 (Avg. rating: 4.5)
• 4 Reviews on Jun 6, 2017 (Avg. rating: 4.5)
• 4 Reviews on Dec 8, 2015 (Avg. rating: 4.0)
• 4 Reviews on Jan 15, 2019 (Avg. rating: 4.0)
• 4 Reviews on Jan 12, 2019 (Avg. rating: 3.8)
Show All

In total, we found that 70 reviews were created on just 15 days. Although any days with a larger number of reviews than expected is suspicious, these reviews do not appear to have a significant impact on the overall rating.

Read more about our Rating Trend test.

• 
• 49%
• 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: 24.1% (Avg. rating: 4.7)
• 41-65 words: 24.5% (Avg. rating: 4.8)

In total, we found that 611 reviews (or 49%) are within an overrepresented word count group. While this is more reviews from overrepresented word count 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 Word Count Comparison test.

• 
• 32%
• 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: 31.7% (Avg. rating: 4.7)

In total, we found that 398 reviewers (or 32%) 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.

• 
• 3%
• Unverified Purchases

34 of the 1,255 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

• 
• 4%
• have only posted one review

45 of the 1,255 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

• 
• 2%
• have zero verified purchases

25 of the 1,255 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

• 
• 1%
• have previously deleted reviews

10 of the 1,255 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

24 of the 1,255 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.

• 
• 2%
• Substantial overlapping review history

26 of the 1,255 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.