Forecast Formula

			Month	Sales
			1	£1,000
			2	£2,000
			3	£2,500
			4	£3,500
			5	£3,800
			6	£4,000
		Type the month number to predict :	12
		The Forecast sales figure is :	£7,997	=FORECAST(E11,F4:F9,E4:E9)
What Does It Do ?
This function uses two sets of values to predict a single value.
The predicted value is based on the relationship between the two original sets of values.
If the values are sales figures for months 1 to 6, (Jan to Jun), you can use the function
to predict what the sales figure will be in any other month.
The way in which the prediction is calculated is based upon the assumption of a Linear Trend.
Syntax
=FORECAST(ItemToForeCast,RangeY,RangeX)
ItemToForecast is the point in the future, (or past), for which you need the forecast.
RangeY is the list of values which contain the historical data to be used as the basis
of the forecast, such as Sales figures.
RangeX is the intervals used when recording the historical data, such as Month number.
Formatting
No special formatting is needed.
Example
The following table was used by a company considering expansion of their sales team.
The Size and Performance of the previous teams over a period of three years were entered.
The size of the New Sales team is entered.
The =FORECAST() function is used to calculate the predicted performance for the new sales
team based upon a linear trend.
	Year	Size Of Sales Team	Known Performance
	1996	10	£5,000
	1997	20	£8,000
	1998	30	£8,500
		Size Of The New Sales Team :	40
		Estimated Forecast Of Performance :	£10,667	=FORECAST(E43,E39:E41,D39:D41)