Time Series (5) Flashcards
What is a time series
A line graph with time plotted on the horizontal axis
What is a general trend
The way data changes over time
What does a trend line show
The general trend of data
How do you plot a trend line by eye
Place the line roughly between the highest and lowest points of the year
What are the three types of trend
Rising trend
Falling trend
Level trend
What are variations in a time series
A general trend
Seasonal variation
What is seasonal variation
Variation in a time series following a regular pattern
E.g seasons of the year
What are moving averages
An average worked out from a given number of successive observations
They cover one full cycle of the seasons - usually calculated over 4 points
How do you plot moving averages
Plot them at the midpoint of the intervals they cover
(If you had four values they would be plotted between two and three)
How do you calculate seasonal variation at a point
Actual value - trend value
What other way (other than by eye) can you draw a trend line on time series
Using the seasonal averages
How do you calculate a seasons mean seasonal variation
Calculate the mean value of all the seasonal variations at one point
How do you calculate a predicted value in time series
Trend line value(at the point you are predicting) + estimate mean seasonal variation
What is another name for the mean seasonal variation
Average seasonal effect
