• 2
• Reviews have been deleted

We discovered a total of 2 deleted Reviews for this product, with an average rating of 4.5. 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

• 
• 16%
• Created over 10 days

We counted 335 reviews for this product over the span of 1,273 days, an average of 0.3 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 10 days exceeding this threshold:

• 8 Reviews on Jan 25, 2019 (Avg. rating: 4.4)
• 7 Reviews on Mar 20, 2019 (Avg. rating: 4.4)
• 6 Reviews on Dec 13, 2018 (Avg. rating: 4.7)
• 6 Reviews on Oct 17, 2018 (Avg. rating: 4.5)
• 5 Reviews on Sep 26, 2018 (Avg. rating: 4.2)
• 4 Reviews on Oct 9, 2018 (Avg. rating: 5.0)
• 4 Reviews on Sep 21, 2018 (Avg. rating: 4.5)
• 4 Reviews on Nov 8, 2018 (Avg. rating: 4.5)
• 4 Reviews on Feb 26, 2019 (Avg. rating: 4.5)
• 4 Reviews on Jul 31, 2018 (Avg. rating: 4.3)
Show All

In total, we found that 52 reviews were created on just 10 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

• 
• 20%
• have only posted one review

67 of the 335 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.

• 
• 70%
• 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: 69.6% (Avg. rating: 4.2)

In total, we found that 233 reviewers (or 70%) 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.

• 
• 17%
• Unverified Purchases

57 of the 335 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.

• 
• 22%
• 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:

• 101-200 words: 21.8% (Avg. rating: 4.4)

In total, we found that 73 reviews (or 22%) are within an overrepresented word count group. 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 Word Count Comparison test.

• 
• 5%
• Substantial overlapping review history

16 of the 335 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

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.