• 1
• Review has been deleted

We discovered a total of 1 deleted Review 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

• 
• 17%
• Created over 19 days

We counted 3,684 reviews for this product over the span of 360 days, an average of 10.2 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 22 or fewer reviews on any given day.

However, we see the following 19 days exceeding this threshold:

• 62 Reviews on Jul 14, 2019 (Avg. rating: 4.1)
• 45 Reviews on Jul 17, 2019 (Avg. rating: 4.6)
• 40 Reviews on Jul 13, 2019 (Avg. rating: 4.3)
• 38 Reviews on Jul 19, 2019 (Avg. rating: 4.1)
• 37 Reviews on Apr 19, 2020 (Avg. rating: 4.7)
• 37 Reviews on May 18, 2020 (Avg. rating: 4.5)
• 36 Reviews on Apr 29, 2020 (Avg. rating: 4.7)
• 36 Reviews on May 17, 2020 (Avg. rating: 4.5)
• 31 Reviews on Apr 30, 2020 (Avg. rating: 4.6)
• 30 Reviews on May 6, 2020 (Avg. rating: 4.5)
• 29 Reviews on Apr 20, 2020 (Avg. rating: 4.5)
• 28 Reviews on May 7, 2020 (Avg. rating: 4.5)
• 26 Reviews on May 27, 2020 (Avg. rating: 4.6)
• 25 Reviews on May 26, 2020 (Avg. rating: 4.7)
• 25 Reviews on May 14, 2020 (Avg. rating: 4.6)
• 25 Reviews on Jul 23, 2019 (Avg. rating: 4.6)
• 25 Reviews on May 8, 2020 (Avg. rating: 4.5)
• 24 Reviews on May 11, 2020 (Avg. rating: 4.2)
• 23 Reviews on Apr 27, 2020 (Avg. rating: 4.4)
Show All

In total, we found that 622 reviews were created on just 19 days. This is an excessively high number of reviews submitted on these high volume days.

Read more about our Rating Trend test.

One-Hit Wonders

• 
• 11%
• have only posted one review

408 of the 3,684 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.

Read more about our Suspicious Reviewers 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 4.3, 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.

• 
• 100%
• 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: 99.6% (Avg. rating: 4.4)

In total, we found that 3,670 reviews (or 100%) 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.

• 
• 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 1-5 Reviews: 49.0% (Avg. rating: 4.4)

In total, we found that 1805 reviewers (or 49%) 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.

• 
• 1%
• Unverified Purchases

24 of the 3,684 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.

• 
• 28%
• Substantial overlapping review history

1,041 of the 3,684 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.

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.