You need to review calls but don’t want to eat into precious time and resources without jeopardising sample quality.
What’s the magic number?
Use this handy free calculator to quickly work out the number of calls that should be reviewed per agent per month in your call center to achieve a statistically valid sample, based on total call volume, number of agents, and desired confidence level.
Call Center Quality Management Sample Size Calculator
Is your optimal sample size larger than you expected? See how we can help.
Factors that will impact your sample size
The smaller your margin of error, the larger your sample size will need to be for the same population.
The higher your confidence level needs to be, the larger your sample size will need to be, too.
Answers to your questions about quality management sample size calculation
How does the calculator work?
The calculator uses a statistical formula to determine the minimum number of calls you need to review per agent to achieve reliable results. It factors in your total call volume, number of agents, and desired confidence level. The formula adjusts for finite populations, so the sample size is accurate even if your call volume isn’t extremely large.
Why is sample size important in call centre quality monitoring?
Sample size ensures your quality monitoring results are representative of overall performance. Reviewing too few calls can lead to biased insights, while an appropriate sample size gives you confidence that your findings reflect reality.
How does sample size affect accuracy or confidence in my results?
A larger sample size reduces the margin of error, making your results more accurate. If your sample is too small, your conclusions may not hold true across all calls, leading to poor decision-making.
How do confidence level and margin of error influence the recommended sample size?
- Confidence level (e.g., 95% or 99%) indicates how sure you are that your sample reflects the true population. Higher confidence requires a larger sample.
- Margin of error is the acceptable range of variation. A smaller margin means more precision, which also increases the sample size.
What if I don’t know my total call volume?
If you don’t know your exact call volume, estimate based on historical data or use an average monthly figure. The more accurate your estimate, the better your sample size calculation will be.
How often should I re-calculate my sample size?
Recalculate whenever your call volume changes significantly, you add or remove agents, or you adjust your confidence level or compliance requirements.
Does the calculator work for both inbound and outbound calls?
Yes. The calculation is based on total call volume and agent count, so it applies to inbound, outbound, or blended call centres.
How should I adjust my sample size if I have strict compliance requirements?
If compliance is critical, consider:
- Using a higher confidence level (e.g., 99% instead of 95%).
- Reducing your margin of error. Both adjustments will increase your sample size, giving you greater assurance of compliance.
What if call quality varies a lot?
Yes. Greater variability means you need a larger sample to capture the full range of performance and avoid skewed results.
Leveraging AI to help with quality management sampling
The manual admin of post-call summary write-ups and subsequent QA reviews is a time and resource drainer for handlers. It also leave a lot of room for human error – missed information, misjudged sentiment, or forgotten entirely. For this reason, many contact and call centers review only a small sample of their interactions, but this often isn’t a sufficient sample size.
We find that for many Quality Analysts, 80% of their time is spent finding the right data and 20% of their time is spent analysing it. We flip this stat on its head and give Analysts more time to analyse, with a larger data sample set, by streamlining their retrieval of the right interaction data. This is because we can import and ingest all of a contact center’s disparate data into one single, secure system and make retrieval and playback much faster for Quality Managers. For a free demo of this, get in touch with our experts here.
