Discuss the trend first.
The trend gives us the general direction in which the data is headed.
The trend is the average of the series data and is determined by a process called 'smoothing'.
Start with an 'eyeball description' of whether the series is increasing, decreasing or remaining constant. This can then be improved by looking at start and end values of the trend line.
Describe these changes in context by stating the rate of change that is occurring.
Remember:
To get higher grades, you need to contextualise your findings.
Once you have performed your analysis, you will need to relate your findings back to the problem you are investigating.
i.e What do the numbers tell you about what is happening in the real world problem you are studying?
Discussing the overall trend involves describing what is happening to the blue line on our recomposed data graphs.
Is it increasing, decreasing or doing something else?
Describe this with numbers. Specify exact locations on the graph with dates to back up your comments.
For higher grades you should be describing the changes in the trend in context and linking it to your purpose. You should always start by stating the start and finish values, and then elaborate on what is happening in between. You could also think about how much of the variation in the raw data is due to the change in this trend.
For each of the graphs write a comment about the long term trend.
The first two have been done for you.
By looking at the long term trend, I can see that overall the amount of sea ice in the artic appears to be generally decreasing from an average of about 9.45 million square kilometres in 1990 to an average of about 8.37 million square kilometres in 2011.
This is an average decrease of (9.45 - 8.37)/21 = 51,400 square kilometres per year (3sf).
This decreasing trend appears to be quite constant, apart from a slight trough between 1995 and 1996.
(Possible contextualisation:
This yearly decrease in sea ice is significant, and could result in observable sea level rises. This could be catastrophic for low lying island nations around the world.)
By looking at the trend line, I can see that overall the amount of male live births has increased since 2000 from an average of about 7400 per quarter to approximately 7800 male live births per quarter at the end of 2012.
This is an average increase of about (7670 - 7400)/12 = 22.5 births per quarter.
In 2000 there were approximately 7400 births per quarter on average, this dropped to approximately 6800 per quarter on average in 2002, climbed to a peak of 8200 per quarter on average in 2008, possibly due to the financial boom, and has dropped off slightly to approximately 7800 per quarter on average in at the end of 2012.