Calculating the Likelihood of an Event

I am working in a Contact Center environment. Have recently implemented a Helpdesk. Estimated the number of Agents required by 15-minute segment based on previous data collected believing it would flow similar to overall call volumes by 15 minute segment.

Based on the above a schedule was designed for the agents.

Collected call termination data (caller hangs up before answered by agent) for the past 34 working days by 15-minute segment. Some have 0 values others have values above that.

What I am trying to determine is what the likelihood is that a specific time segment will experience a call termination due to more calls coming in than there are agents to answer on an average day.

This would allow us to determine if we need to change schedules.

I am not sure what tool to use to analyze this count data

Data currently resides in Excel with rows being the 15 minute segment and the top row being the date

I use Mini-tab 13

Thanks, John