In a two hour charity 'dance-a-thon' dancers can join and leave the dance floor as they choose.
The number of dancers on the dance floor is recorded every 15 minutes.
The times-series graph below shows the data for the first two hours of the 'dance-a-thon'.
At 1 h 45 m and 2 h the number of dancers were 3 and 6 respectively.
Add these two recordings to the time-series graph.
Plot the points 105 minutes (1 h 45 m) on the time axis against 3 on the number of dancers axis and 120 minutes against 8 dancers.
Use the time-series graph to find
the time at which there were the fewest number of dancers,
the two times at which the number of dancers remained the same.
Look for the lowest point on the graph, including those added in part a).
The lowest point is (105, 3)
The final answer is the time.
105 minutes (1 h 45 m)
The keyword here is remain - a horizontal line would indicate the number of dancers remaining the same.
There is a horizontal line between 45 and 60 minutes
The number of dancers remained the same at 45 m and 60 m (1 h)
Comment on the general pattern of the number of dancers shown by the time-series graph.
Apart from the last point, and where it remained the same, the number of dancers decreased over the two hours.
In general, the number of dancers decreased during the first two hours of the 'dance-a-thon'
Avoid speculating on why this might be - e.g. DO NOT write "people get tired".
If a question wants you to do this, it will use phrases like "suggest a reason for ..." or similar.