An overall average time till the first response report can be generated using the DPQL below:

SELECT AVG(tickets.total_to_first_reply / 3600) AS 'Average first response time in hours'
FROM tickets

For a specific timeframe, a variable can be added, which allows the flexibility of choosing a specific timeframe. This can be done by first clicking on  'Add Variable' and filling in the details  as follows:

Once the variable is added, you could add a WHERE clause, which is used to limit the data displayed or used. In this example, a DPQL form can be written as shown below:

SELECT AVG(tickets.total_to_first_reply / 3600) AS 'Average first response time in hours'
FROM tickets
WHERE tickets.date_created = ${date}

This data can be further grouped by agent, as shown below:  

SELECT AVG(tickets.total_to_first_reply / 3600) AS 'Average first response time in hours'
FROM tickets
WHERE tickets.date_created = ${date}
GROUP BY tickets.agent