• 
• 3%
• Created over 4 days

We counted 485 reviews for this product over the span of 2,628 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 4 days exceeding this threshold:

• 4 Reviews on Apr 25, 2020 (Avg. rating: 3.8)
• 4 Reviews on May 17, 2020 (Avg. rating: 3.5)
• 4 Reviews on May 10, 2016 (Avg. rating: 3.3)
• 4 Reviews on Jul 19, 2017 (Avg. rating: 3.0)

In total, we found that 16 reviews were created on just 4 days. The reviews on these high volume days have rated this product an average of 3.4 while reviews from other days have rated this product an average of 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.

Read more about our Rating Trend test.

Never-Verified Reviewers

• 
• 3%
• have zero verified purchases

15 of the 485 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 4.1. 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.

• 3
• Reviews have been deleted

We discovered a total of 3 deleted Reviews for this product, with an average rating of 4. 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

• 
• 98%
• 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:

• 0-5 words: 100.0% (Avg. rating: 3.6)
• 0-5 words: 97.5% (Avg. rating: 4.1)

In total, we found that 473 reviews (or 98%) 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.

• 
• 32%
• From reviewers with an overrepresented participation

We see the following 2 participation groups with a statistically significant greater concentration than what we'd expect to see:

• Reviewers with 1-5 Reviews: 75.0% (Avg. rating: 3.8)
• Reviewers with 1-5 Reviews: 31.8% (Avg. rating: 4.2)

In total, we found that 154 reviewers (or 32%) are within an overrepresented participation group. While this is more reviews from overrepresented participation groups than we'd expect to see, the discrepancy in ratings between reviewers in an overrepresented participation groups and all other reviewers isn’t significant enough to rule out the possibility of it being due to random chance.

Read more about our Reviewer Participation test.

• 
• 5%
• Unverified Purchases

23 of the 485 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.

• 
• 10%
• Substantial overlapping review history

50 of the 485 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 4.2, while the average ease score for reviewers in this category is 4.2.

Brand Repeaters

• 
• 8%
• Reviewed other products from this brand

39 of the 485 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.

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.