Operating System Concepts, 9th Edition
More product info
From Abraham Silberschatz
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Report Card
Most Trusted Reviews
TRUST
- Verified Purchaser
- Overlapping Review History: reviewed 2 of 9 top products
- Critical Reviewer (avg. rating: 4.0)
Least Trusted Reviews
TRUST
- Unverified Purchaser
- Contains repetitive phrases (show)
- Take-Back Reviewer (2 deleted Reviews; avg. rating: 1.0)
- Overrepresented Participation (posted 9 Reviews)
- Critical Reviewer (avg. rating: 3.0)
Analysis Details
We discovered a total of 14 deleted Reviews for this product, with an average rating of 3.5. 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:
- 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.
89 of the 230 total reviews for this product are unverified purchases. The unverified purchasers have rated this product an average of 3.3 while the verified purchasers have rated this product an average of 4.1. 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
23 of the 230 reviewers have only reviewed this product. While this is more One-Hit Wonders than we'd expect to see, the discrepancy in ratings between the One-Hit Wonders and reviewers who have posted more than one review isn't significant enough to rule out the possibility of it being due to random chance.
Take-Back Reviewers
22 of the 230 reviewers have had at least one of their past reviews for another product deleted. While this is more Take-Back Reviewers than we'd expect to see, the discrepancy in ratings between the Take-Back Reviewers and reviewers who don't have any deleted reviews in their history isn't significant enough to rule out the possibility of it being due to random chance.
Single-Day Reviewers
4 of the 230 reviewers have written multiple reviews but posted all of them on a single day. The Single-Day reviewers have rated this product an average of 5.0 while all other reviewers 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.
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- 6%
- Created over 7 days
We counted 230 reviews for this product over the span of 7,724 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 1 or fewer reviews on any given day.
However, we see the following 7 days exceeding this threshold:In total, we found that 14 reviews were created on just 7 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.
(4.3/5)
(5.0/5)
(3.8/5)
(3.9/5)
(4.2/5)
(5.0/5)
(3.5/5)
(4.2/5)
(3.8/5)
(4.0/5)
46 of the 230 total reviews for this product use substantial repetitive phrases between them. This is an excessively large percentage which may indicate unnatural reviews.
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- 68%
- From reviewers with an overrepresented participation
We see the following 2 participation groups with a statistically significant greater concentration than what we'd expect to see:In total, we found that 156 reviewers (or 69%) are within an overrepresented participation group. This is an excessively high number of reviewers in overrepresented participation groups.
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- 0%
- Have an overrepresented word count
Read more about our Word Count Comparison test.
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34 of the 230 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.
4.0 Product's Average Ease Score
4.3 Category's Average Ease Score
Read more about our Reviewer Ease test.
Brand Repeaters
3 of the 230 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.