• 
• 5%
• Unverified Purchases

25 of the 513 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 4.8 while the verified purchasers 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.

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

• 
• 19%
• have only posted one review

96 of the 513 reviewers have only reviewed this product. The One-Hit Wonders have rated this product an average of 4.7 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.

Read more about our Suspicious Reviewers test.

• 
• 61%
• 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: 60.8% (Avg. rating: 4.5)

In total, we found that 312 reviewers (or 61%) 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 4.3. 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 Reviewer Participation test.

• 17
• Reviews have been deleted

We discovered a total of 17 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

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 4.3, 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.

• 
• 99%
• 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: 98.8% (Avg. rating: 4.4)

In total, we found that 507 reviews (or 99%) 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.

• 
• 0%
• Created on high-volume days

We counted 513 reviews for this product over the span of 478 days, an average of 1.1 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 6 or fewer reviews on any given day. We didn't find any days exceeding this threshold.
Read more about our Rating Trend test.

• 
• 0%
• Substantial overlapping review history

0 of the 513 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

• 
• 1%
• Reviewed other products from this brand

4 of the 513 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.