• 384
• Reviews have been deleted

We discovered a total of 384 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

• 
• 33%
• Created over 39 days

We counted 2,199 reviews for this product over the span of 665 days, an average of 3.3 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 11 or fewer reviews on any given day.

However, we see the following 39 days exceeding this threshold:

• 31 Reviews on Dec 11, 2018 (Avg. rating: 4.3)
• 29 Reviews on Dec 13, 2018 (Avg. rating: 3.4)
• 28 Reviews on Dec 12, 2018 (Avg. rating: 3.8)
• 27 Reviews on Dec 14, 2018 (Avg. rating: 4.1)
• 26 Reviews on Dec 16, 2018 (Avg. rating: 4.1)
• 26 Reviews on Dec 24, 2018 (Avg. rating: 4.0)
• 25 Reviews on Dec 10, 2018 (Avg. rating: 3.9)
• 24 Reviews on Dec 15, 2018 (Avg. rating: 4.0)
• 23 Reviews on Dec 22, 2018 (Avg. rating: 4.2)
• 23 Reviews on Dec 27, 2018 (Avg. rating: 3.9)
• 21 Reviews on Jan 5, 2019 (Avg. rating: 4.5)
• 21 Reviews on Dec 17, 2018 (Avg. rating: 4.0)
• 21 Reviews on Dec 23, 2018 (Avg. rating: 4.0)
• 20 Reviews on Jan 4, 2019 (Avg. rating: 3.8)
• 19 Reviews on Jul 16, 2019 (Avg. rating: 3.8)
• 19 Reviews on Jan 13, 2019 (Avg. rating: 3.4)
• 18 Reviews on Jan 8, 2019 (Avg. rating: 3.6)
• 17 Reviews on Jul 17, 2019 (Avg. rating: 4.2)
• 17 Reviews on Dec 18, 2018 (Avg. rating: 3.7)
• 17 Reviews on Jan 9, 2019 (Avg. rating: 3.5)
• 16 Reviews on Jan 12, 2019 (Avg. rating: 3.9)
• 16 Reviews on Dec 29, 2018 (Avg. rating: 3.8)
• 16 Reviews on Dec 25, 2018 (Avg. rating: 3.7)
• 15 Reviews on Jan 20, 2019 (Avg. rating: 4.4)
• 15 Reviews on Jul 15, 2019 (Avg. rating: 3.8)
• 15 Reviews on Jan 10, 2019 (Avg. rating: 3.7)
• 15 Reviews on Jan 2, 2019 (Avg. rating: 3.6)
• 15 Reviews on Jan 14, 2019 (Avg. rating: 3.3)
• 15 Reviews on Dec 9, 2018 (Avg. rating: 3.2)
• 14 Reviews on Dec 21, 2018 (Avg. rating: 3.9)
• 13 Reviews on Jan 23, 2019 (Avg. rating: 4.2)
• 13 Reviews on Jan 6, 2019 (Avg. rating: 4.1)
• 13 Reviews on Jan 7, 2019 (Avg. rating: 3.9)
• 12 Reviews on Dec 7, 2018 (Avg. rating: 4.6)
• 12 Reviews on Jan 17, 2019 (Avg. rating: 4.3)
• 12 Reviews on Jan 26, 2019 (Avg. rating: 4.1)
• 12 Reviews on Jan 25, 2019 (Avg. rating: 3.9)
• 12 Reviews on Feb 18, 2019 (Avg. rating: 3.6)
• 12 Reviews on Mar 22, 2019 (Avg. rating: 3.4)
Show All

In total, we found that 715 reviews were created on just 39 days. The reviews on these high volume days have rated this product an average of 3.9 while reviews from other days have rated this product an average of 3.7. 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

• 
• 25%
• have only posted one review

548 of the 2,199 reviewers have only reviewed this product. While this is more One-Hit Wonders than we'd expect to see, it does not appear to have a significant impact on the overall rating.

Take-Back Reviewers

• 
• 3%
• have previously deleted reviews

56 of the 2,199 reviewers have had at least one of their past reviews for another product deleted. The Take-Back Reviewers have rated this product an average of 4.5 while the reviewers who don't have any deleted reviews in their history have rated this product an average of 3.8. 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.

• 
• 11%
• Substantial overlapping review history

236 of the 2,199 reviewers have substantial overlapping product review history. These reviewers have rated this product an average of 4.8 while the reviewers who have a more unique product review history rated this product an average of 3.7. 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 Overlapping Review History test.

Brand Loyalists

• 
• 2%
• Reviewed mostly products from this brand

49 of the 2,199 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.

• 
• 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 1 group with a statistically significant greater concentration than what we'd expect to see:

• 0-5 words: 98.2% (Avg. rating: 3.8)

In total, we found that 2,160 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.

• 
• 63%
• 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: 63.4% (Avg. rating: 3.7)

In total, we found that 1395 reviewers (or 63%) are within an overrepresented participation group. This is an excessively high number of reviewers in overrepresented participation groups.

Read more about our Reviewer Participation test.

• 
• 11%
• Unverified Purchases

232 of the 2,199 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.

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

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.