Long Term Trend

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?

Long Term Trend line.
This is an average value.
The average is calculated over the period of one complete cycle.
eg. The value 9.45 in the time series graph above represents the average amount of sea ice over a year.
Start value of long term trend.
End value of long term trend.

Use the start and end points to describe the overall change.
i.e Is it increasing, decreasing or staying the same?
What is the average rate of change of the variable per week, per month, per year, etc
To add depth to your analysis and improve the quality of your report, you should also describe any interesting variations of the trend line between the start and end points.
Describe peaks, troughs, sudden shifts (ramps), etc.
Try and quantify your descriptions as much as possible.
i.e Use numbers.

Example of Long Term Trend description

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.)

Written Report (so far)

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