What kind of things do we have to write about when describing a time series plot and a smoothed time series plot? What kind of things about the graph should we focus on? Also do we have to write our descriptions in any specific way?
Hey! When describing a time series plot you should talk about:
- Trends (positive/upward? negative/downwards? no trend?)
- Are there any irregular or random fluctuations?(short term fluctuations) or is the time series fairly predictable? I also used to point out the degree e.g "there is small amount of random fluctuations in this time series"
- Is there seasonal variation? These are usually easy to spot, look for peaks and lows (cyclical) occurring around the same time (e.g a time series of a week and general peaks on thursdays but lows on fridays). But remember seasonal variation must be within one calendar year. For example you can say "peaks are generally during the month of January over the years" however you cannot say "Peaks during every second year e.g peaks in the year 1995, 1997, 1999" as this is more than one calendar year (hopefully this makes sense!)
- Is there any structural change? Probably the hardest to spot, but it is when something big happens and changes the pattern of the plot. E.g if there is a general upward trend, then suddenly there is a downward trend on the plot, you could say this is structural change. There is more than one trend visible on the plot! Don't confuse this with irregular fluctuations as this is LONG TERM whereas irregular fluctuations are SHORT TERM and are outliers.
The wording can be tricky but something nice, simple and straight to the point makes the examiners happy! Something like, "In this time series, we can see a steep upward trend with seasonal variation (as there are peaks every January and lows every March). There is some slight irregular fluctuations, and some outliers at the point (x, y, z).
Hope this helps! Good luck!
Home
Help
Search
Login
