Given that Sedlacek and his colleagues have conducted many studies using the NCQ in the last three decades, it is surprising that relatively little information about the reliability and validity of the NCQ is provided in this book.
The NCQ appears to be a good predictor of student persistence and notably, it is more effective in predicting persistence for Black students than for White students (Tracey & Sedlacek, 1984a, 1985, 1987).
Since then, this same item has been used in NCQ models to assess "fair academic opportunity" (Tracey & Sedlacek, 1984a), positive self-concept (Tracey & Sedlacek, 1987), long-range goals (Tracey & Sedlacek, 1987), academic ability (Tracey & Sedlacek, 1987), and realistic self-appraisal (Tracey & Sedlacek, 1988).
He offers the following summary of construct validity as it pertains to the NCQ: "Tracey and Sedlacek (1984a, 1984b), Woods and Sedlacek (1988), and Ting and Sedlacek (2000) presented construct validity evidence for scores on the eight dimensions measured by the NCQ for African American and White samples (see Appendix 2)" (p.
More specifically, NCQ increases performance and disc drive life by allowing the drive to internally optimize the execution order of workloads or commands.
For system builders, NCQ offers a way to easily scale high-capacity Serial ATA disc for use in desktop PCs to high performance PCs, workstations and entry servers--and at just pennies per Gigabyte.
NCQ drives have an internal queue where these unsent commands, along with mechanisms that track outstanding and completed portions of the workload, are rescheduled or re-ordered.
NCQ reduces the rotation latency by processing more IOPS with fewer disc revolutions.
The hard drive on the left, with NCQ, can execute four commands (A, B, C, and D) with one and a quarter complete rotations due to proper ordering of the operations.
In summary, if you need more performance and improved reliability, a NCQ system design is your ticket.