• 
• 89%
• Unverified Purchases

526 of the 588 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 4.6 while the verified purchasers have rated this product an average of 4.0. 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.

On Oct 3, 2016, Amazon prohibited incentivized reviews, however we still test for them since there are still millions in our dataset.

• 
• 70%
• Admitted to receiving an incentive

413 of the 588 total reviews for this product admitted to receiving a free or discounted product in exchange for a review. Incentivized reviews have rated this product an average of 4.6 while reviews that were not incentivized 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 Incentivized Reviews test, or check out our study showing that Incentivized Reviewers are much more likely to leave a positive review.

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

• 
• 62%
• Used substantial repetitive phrases

364 of the 588 total reviews for this product use substantial repetitive phrases between them. These reviewers have rated this product an average of 4.7 while reviews without substantial repetitive phrases 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 Phrase Repetition test.

• 
• 15%
• Created over 9 days

We counted 588 reviews for this product over the span of 293 days, an average of 2.0 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 8 or fewer reviews on any given day.

However, we see the following 9 days exceeding this threshold:

• 12 reviews on Jan 18, 2016 (Avg. rating: 4.0)
• 10 reviews on Jan 10, 2016 (Avg. rating: 4.9)
• 10 reviews on Jan 14, 2016 (Avg. rating: 4.9)
• 10 reviews on Jan 19, 2016 (Avg. rating: 4.8)
• 10 reviews on Mar 14, 2016 (Avg. rating: 4.3)
• 9 reviews on Jan 7, 2016 (Avg. rating: 5.0)
• 9 reviews on Jan 13, 2016 (Avg. rating: 5.0)
• 9 reviews on Jan 12, 2016 (Avg. rating: 4.9)
• 9 reviews on Jan 15, 2016 (Avg. rating: 4.0)
Show All

In total, we found that 88 reviews were created on just 9 days. Although any days with a larger number of reviews than expected is suspicious, the discrepancy in ratings from reviews created on these high volume days and reviews created on other days isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Rating Trend test.

Brand Repeaters

• 
• 67%
• Reviewed other products from this brand

20 of a random sample of 30 reviewers have reviewed other products for this brand. While this is more Brand Repeaters than we'd expect to see, the discrepancy in ratings between the Brand Repeaters and non-repeaters isn't significant enough to rule out the possibility of it being due to random chance.

Read more about our Brand Repeats test.

• 
• 97%
• Substantial overlapping review history

29 of a random sample of 30 reviewers have substantial overlapping product review history. This is an excessively large percentage which may indicate unnatural reviews.

Read more about our Overlapping Review History test.

• 
• 30%
• 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: 29.8% (Avg. rating: 4.6)

In total, we found that 175 reviews (or 30%) 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.

One-Hit Wonders

We didn't detect a substantial amount of One Hit Wonders.

Never-Verified Reviewers

• 
• 3%
• have zero verified purchases

1 of a random sample of 30 reviewers has never written a verified purchase review. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

Take-Back Reviewers

We didn't detect a substantial amount of Take-Back Reviewers.

Single-Day Reviewers

We didn't detect a substantial amount of Single-Day Reviewers.

• 
• 0%
• From reviewers with an overrepresented participation

We didn't find any participation groups that had a statistically significant greater concentration than what we'd expect to see in this category.
Read more about our Reviewer Participation test.

• 0
• Reviews have been deleted

We have not discovered any deleted reviews for this product.

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 the Deleted Reviews test here.