^
Forecasting techniques:
] Y – the experimental value of the analyzed variable
Y – the predicted value of the analyzed variable
t – index to distinguish periods
^
Y t+1 = Y t
^
Proportionaly - changing model
The value of a variable changes from current to next period will be proportional to the value of a variable changes from the previous period to the current period
Y t+1 = Y t + k ∆ Y t
^
Evaluation of k based on retrospective information.
K = 1 is a uniformly changing the model
For most short-term predictions the simplest models are the most easy ways of forecasting, since they are easy to use and requires minimal information for calculating
Mechanical extrapolation
Forecasting techniques:
The simplest models:
Guidelines for decision :
1. The forecast value of the parameter on the basis of extrapolation in the current average annual growth rate is determined by the formula
Кn+1 – the forecast value of the parameter;
Кn – parameter value in the reporting period;
Тср.г. – the average annual rate of growth of parameter.
Тц1, Тц2,…,Тцn – the parameter of chain growth for periods; n is the number of periods.
4. The rate of growth, like a chain, and the average, characterize the relative rate of change of the level of series during the relevant period (or unit time)
Тпр.ц – chain increment rate;
Тц – chain growth rate.
Тпр.ср.г. – chain increment rate;
Тср.г. – среднегодовой темп роста.
Ordered in time indicators: sales, production volume, prices….
Mechanical extrapolation
Forecasting techniques:
Time series analysis:
Mechanical extrapolation
Forecasting techniques:
Due to weather conditions and habits appear almost at the same time of a year (for example, New Year, Easter and other holidays, during which various purchases are made)
Time series analysis:
Mechanical extrapolation
Forecasting techniques:
Irregular forces (I)
Strikes, war. Inconsistent in their effect on individual series, but, nevertheless, be taken into account
Time series analysis:
Mechanical extrapolation
Forecasting techniques:
Seasonal changes can be taken into account in the forecast using the seasonal index, which can be calculated by the method of moving average
Time series analysis:
Mechanical extrapolation
Forecasting techniques:
Volume of sales
quarter
total
Each subsequent calculation does not include the first quarter and adds the next quarter
Step 2: Centralized moving average for each quarter is calculated as the average of each consecutive pair of 4-period moving averages
Step 3: Seasonal indexes are calculated by dividing the actual volume of sales for the corresponding quarter by centralized moving average for the same period
Step 4: arrange seasonal indexes quarterly
quarter
Year
Sales
4-period
moving
average
centralized
moving
average
Seasonal
index
Average value is 1.01: adjust seasonal indices up or down, revealing trends and maintaining the average value of the four indexes equal to 1
0,99 1,38 0,98 0,65
Year
Average Seasonal index
total
Data to calculate Seasonal indexes
Average Seasonal index
0,99 1,38 0,98 0,65
4-period
moving
average
centralized
moving
average
Seasonal
index
Sales
Step 6: preparation of the forecast for each quarter of the coming year: multiply the last centered moving average for the quarter by its seasonal index
quarter
Year
The most widely used method of trend detection is regression analysis, namely the method of least squares
The method consists of the selection of a regression line according to the observations so that the squares of their deviations from the regression line were minimal
Time series analysis:
Mechanical extrapolation
Forecasting techniques:
^
Regression line is presented by: Y = a + bt, where a and b - parameters of evaluation, t – number of period
^
To find the values of the parameters a and b, it is necessary to solve the system of equations
Seasonal effects are smoothed by a moving average
Forecasting techniques:
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