Koss QZ-99 Noise Reduction Stereophone Headphones
More product info
From Koss
Refresh the report to view the most up-to-date data available:
Note: We only analyze "reviews" and ignore one-tap "ratings".
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Most Trusted Reviews
TRUST
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Verified Purchaser
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Easy Grader (avg. rating: 4.3)
Least Trusted Reviews
TRUST
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Verified Purchaser
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Take-Back Reviewer (2 deleted Reviews; avg. rating: 3.5)
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Brand Repeater (2 of 174 reviews for this brand; avg rating: 4.0)
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Easy Grader (avg. rating: 4.4)
Analysis Details

Take-Back Reviewers
121 of the 357 reviewers have had at least one of their past reviews for another product deleted. The Take-Back Reviewers have rated this product an average of 4.1 while the reviewers who don't have any deleted reviews in their history have rated this product an average of 3.8. 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.

We discovered a total of 7 deleted Reviews for this product, with an average rating of 3.6. 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:
- 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.
- We have no information on reviews that were never published in the first place.
- 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.

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- 1%
- Created over 1 day
We counted 357 reviews for this product over the span of 7,232 days, an average of 0.0 reviews per day. If these reviews were created randomly, there would be a 99.9% chance that we would see 2 or fewer reviews on any given day.
However, we see the following 1 day exceeding this threshold:In total, we found that 3 reviews were created on just 1 day. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

31 of the 357 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.

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- 0%
- Have an overrepresented word count
Read more about our Word Count Comparison test.

(3.7/5)
(4.3/5)
(4.1/5)
(3.9/5)
(3.8/5)
(5.0/5)
(4.3/5)
(4.3/5)
(3.9/5)
(3.7/5)
31 of the 357 total reviews for this product use substantial repetitive phrases between them. This is within an acceptable range and it does not appear to be significantly affecting the overall rating for this product.

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41 of the 357 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.

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- 0%
- From reviewers with an overrepresented participation
Read more about our Reviewer Participation test.

4.1 Product's Average Ease Score
4.3 Category's Average Ease Score
Read more about our Reviewer Ease test.

Brand Repeaters
17 of the 357 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.

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- 0%
- Admitted to receiving an incentive
Read more about our Incentivized Reviews test. Check out our study showing that Incentivized Reviewers are much more likely to leave a positive review.