Let's analyze the average time on hold in the given intervals to determine when the average time spent on hold increased.
### Interval from Week 1 to Week 3:
- Average time on hold in Week 1: 7 minutes
- Average time on hold in Week 3: 3 minutes
Change in time [tex]\( \Delta t_{1\rightarrow3} = 3 - 7 = -4 \)[/tex]
Since the change is negative, the time on hold decreased between Week 1 and Week 3.
### Interval from Week 1 to Week 4:
- Average time on hold in Week 1: 7 minutes
- Average time on hold in Week 4: 2 minutes
Change in time [tex]\( \Delta t_{1\rightarrow4} = 2 - 7 = -5 \)[/tex]
Since the change is negative, the time on hold decreased between Week 1 and Week 4.
### Interval from Week 4 to Week 6:
- Average time on hold in Week 4: 2 minutes
- Average time on hold in Week 6: 5 minutes
Change in time [tex]\( \Delta t_{4\rightarrow6} = 5 - 2 = 3 \)[/tex]
Since the change is positive, the time on hold increased between Week 4 and Week 6.
### Interval from Week 3 to Week 5:
- Average time on hold in Week 3: 3 minutes
- Average time on hold in Week 5: 3 minutes
Change in time [tex]\( \Delta t_{3\rightarrow5} = 3 - 3 = 0 \)[/tex]
Since the change is zero, the time on hold did not increase between Week 3 and Week 5.
Based on this analysis, the interval during which the average time spent on hold increased is:
- Week 4 to Week 6
