CWS Research Methods & Evidence-Based Practice 3 — Questions and Answers
Question 1: During a wireless network assessment, you collect throughput data at 30 locations. The results are heavily skewed by three locations with unusually low values. Which measure of central tendency BEST represents typical network performance?
- Mean
- Median (Correct answer)
- Mode
- Range
Correct answer: Median
The median is resistant to outliers, making it the best representation of typical performance when extreme low values skew the distribution.
Question 2: An engineer performs both passive and active surveys at the same location. The passive survey shows strong RSSI, but the active survey reveals low throughput. What is the MOST likely explanation?
- The passive survey sensor has a miscalibrated antenna
- Hidden node interference or high retry rates are degrading actual link performance (Correct answer)
- The active survey client is using an outdated 802.11n driver
- The channel width setting differs between the two survey tools
Correct answer: Hidden node interference or high retry rates are degrading actual link performance
Strong RSSI with poor throughput typically indicates MAC-layer issues like excessive retries caused by hidden nodes or high interference, not physical signal weakness.
Question 3: When using iPerf3 to benchmark wireless throughput, running the test in which direction provides the MOST insight into uplink performance for VoIP quality assessment?
- Server to client (downlink)
- Client to server (uplink) (Correct answer)
- Bidirectional simultaneous
- Reverse mode with UDP protocol
Correct answer: Client to server (uplink)
For VoIP, uplink performance is critical because voice from the client to the server must be assessed; running iPerf3 client-to-server measures this direction.
Question 4: A wireless engineer finds that channel utilization consistently exceeds 70% in a high-density auditorium. What evidence-based design change is MOST appropriate?
- Reduce the number of APs to lower the number of BSSIDs
- Increase AP transmit power to override the interference
- Add APs on non-overlapping channels to distribute the load (Correct answer)
- Widen channel width from 20 MHz to 40 MHz to increase capacity
Correct answer: Add APs on non-overlapping channels to distribute the load
Adding APs on non-overlapping channels distributes client load and reduces per-AP utilization, which is the evidence-based solution for channel saturation.
Question 5: Which protocol capture filter would BEST isolate 802.11 management frames to analyze roaming behavior in a Wireshark capture?
- wlan.fc.type == 2
- wlan.fc.type == 0 (Correct answer)
- wlan.fc.type == 1
- wlan.fc.ds == 1
Correct answer: wlan.fc.type == 0
In 802.11, frame type 0 designates management frames, which include probe requests/responses, association, and authentication frames used during roaming.
Question 6: A network team wants to establish a repeatable benchmarking methodology for quarterly wireless performance reviews. Which approach BEST ensures result comparability over time?
- Use the same physical test locations, client device, tool versions, and time of day for each assessment (Correct answer)
- Run tests at random locations each quarter to capture a broader sample
- Use different client devices each quarter to average out hardware bias
- Only conduct tests during peak hours when interference is highest
Correct answer: Use the same physical test locations, client device, tool versions, and time of day for each assessment
Consistent test locations, devices, tools, and timing control variables, making quarter-over-quarter comparisons statistically valid.
Question 7: What is the PRIMARY purpose of a spectrum analysis walk-through BEFORE a predictive wireless design is finalized for a new building?
- To identify the optimal AP placement using the spectrum analyzer's mapping feature
- To detect existing non-Wi-Fi RF sources that the predictive model would not account for (Correct answer)
- To measure the 5 GHz channel capacity needed for Wi-Fi 6 deployment
- To verify that the building's structural drawings match the physical layout
Correct answer: To detect existing non-Wi-Fi RF sources that the predictive model would not account for
Pre-design spectrum analysis identifies non-Wi-Fi interferers (DECT phones, Bluetooth devices, microwave ovens, radar) that RF planning tools cannot model.
CWS Research Methods & Evidence-Based Practice 3
During a wireless network assessment, you collect throughput data at 30 locations.
The results are heavily skewed by three locations with unusually low values.
Which measure of central tendency BEST represents typical network performance?