• 88
• Reviews have been deleted

We discovered a total of 88 deleted Reviews for this product, with an average rating of 5. 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

• 
• 6%
• Created over 10 days

We counted 854 reviews for this product over the span of 1,685 days, an average of 0.5 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 4 or fewer reviews on any given day.

However, we see the following 10 days exceeding this threshold:

• 7 Reviews on Mar 15, 2019 (Avg. rating: 4.4)
• 5 Reviews on Jan 27, 2019 (Avg. rating: 5.0)
• 5 Reviews on Feb 22, 2019 (Avg. rating: 5.0)
• 5 Reviews on Apr 7, 2019 (Avg. rating: 5.0)
• 5 Reviews on Sep 29, 2015 (Avg. rating: 4.8)
• 5 Reviews on Aug 4, 2018 (Avg. rating: 4.8)
• 5 Reviews on Jan 24, 2019 (Avg. rating: 4.8)
• 5 Reviews on Dec 19, 2018 (Avg. rating: 4.6)
• 5 Reviews on Feb 26, 2019 (Avg. rating: 4.4)
• 5 Reviews on Apr 20, 2019 (Avg. rating: 3.4)
Show All

In total, we found that 52 reviews were created on just 10 days. The reviews on these high volume days have rated this product an average of 4.6 while reviews from other days have rated this product an average of 4.3. 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 Rating Trend test.

One-Hit Wonders

• 
• 4%
• have only posted one review

34 of the 854 reviewers have only reviewed this product. The One-Hit Wonders have rated this product an average of 3.5 while the reviewers who have posted more than one review have rated this product an average of 4.4. 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.

Never-Verified Reviewers

• 
• 1%
• have zero verified purchases

10 of the 854 reviewers have never written a verified purchase review. The Never-Verified Reviewers have rated this product an average of 3.4 while the reviewers who have written at least one verified purchase review rated this product an average of 4.4. 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

• 
• 0%
• have posted all their reviews on a single day

4 of the 854 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 2.3 while all other reviewers rated this product an average of 4.4. 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.

• 
• 52%
• 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:

• 41-65 words: 29.6% (Avg. rating: 4.4)
• 66-100 words: 22.5% (Avg. rating: 4.7)

In total, we found that 445 reviews (or 52%) are within an overrepresented word count group. These reviews have rated this product an average of 4.5, while all other reviews 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 Word Count Comparison test.

• 
• 10%
• Substantial overlapping review history

82 of the 854 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 4.3. 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 Overlapping Review History test.

• 
• 49%
• 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 6-15 Reviews: 49.3% (Avg. rating: 4.5)

In total, we found that 421 reviewers (or 49%) are within an overrepresented participation group. These reviews have rated this product an average of 4.5, while all other reviews 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 Reviewer Participation 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 4.4, while the average ease score for reviewers in this category is 4.2. While this discrepancy is rather large, it is not quite large enough to rule out the possibility of it being due random chance.

• 
• 4%
• Unverified Purchases

38 of the 854 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.

Brand Repeaters

• 
• 2%
• Reviewed other products from this brand

19 of the 854 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.