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#1
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Trend Function
I have some merchandise that I am trying to determine what the sales trend
is going to be for the next three months. I want this based off of the 24 months worth of sales I have. My sheet has sales for the last 24 months, month by month. Month Sales 1 3 2 4 3 5 4 6 5 7 6 8 7 8 8 7 9 6 10 5 11 4 12 3 13 3 14 4 15 5 16 6 17 7 18 8 19 8 20 7 21 6 22 5 23 4 24 3 25 26 27 I am trying to use the TREND function. For example if my sales were this I would expect the result for month 25 to be 3, if month 1 & 13 represented January. The result I get is 5.5 which is nothing more than the average of all 24 months. T.I.A. |
#2
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Trend Function
Look at teh FORECAST function and see if it suits your needs.
Dave -- Brevity is the soul of wit. "Grant" wrote: I have some merchandise that I am trying to determine what the sales trend is going to be for the next three months. I want this based off of the 24 months worth of sales I have. My sheet has sales for the last 24 months, month by month. Month Sales 1 3 2 4 3 5 4 6 5 7 6 8 7 8 8 7 9 6 10 5 11 4 12 3 13 3 14 4 15 5 16 6 17 7 18 8 19 8 20 7 21 6 22 5 23 4 24 3 25 26 27 I am trying to use the TREND function. For example if my sales were this I would expect the result for month 25 to be 3, if month 1 & 13 represented January. The result I get is 5.5 which is nothing more than the average of all 24 months. T.I.A. |
#3
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Trend Function
Grant -
When working with time series data, the first step is to "look at the data" to identify patterns. Then choose an appropriate model. And finally use Excel to fit an equation. The TREND and FORECAST worksheet functions are usually used to determine long-run average behavior. For your obviously-manufactured data, there is no upward or downward trend, and the TREND and AVERAGE functions do describe the long-run behavior. But a plot shows a strong repetitive pattern, and the obvious forecast for your obviously-manufactured data is 3,4,5 for months 25,26,27. When the time series data show strong repetitive patterns, the appropriate model often incorporates seasonality. Chapter 20, Time Series Seasonality, of my book, Data Analysis Using MS Excel, has step-by-step instructions for three models: indicator variables, autoregression, and classical time series decomposition. - Mike http://www.mikemiddleton.com "Grant" wrote in message ... I have some merchandise that I am trying to determine what the sales trend is going to be for the next three months. I want this based off of the 24 months worth of sales I have. My sheet has sales for the last 24 months, month by month. Month Sales 1 3 2 4 3 5 4 6 5 7 6 8 7 8 8 7 9 6 10 5 11 4 12 3 13 3 14 4 15 5 16 6 17 7 18 8 19 8 20 7 21 6 22 5 23 4 24 3 25 26 27 I am trying to use the TREND function. For example if my sales were this I would expect the result for month 25 to be 3, if month 1 & 13 represented January. The result I get is 5.5 which is nothing more than the average of all 24 months. T.I.A. |
#4
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Trend Function
Often statistics only serve to confuse. I would guess that these are quite
high value items, otherwise you would not be too bothered about them. You have very few numbers to base a forecast on. If you have many different customers and there are a large number of potential customers then a reliable forecast might be impossible. If you have only a small number of customers you might get a better idea by ringing some of them up, asking such things as how they got on with your product, how it compared to competitors, any suggestions for improvements, and, BTW, are you in the market for more soon? "Grant" wrote in message ... I have some merchandise that I am trying to determine what the sales trend is going to be for the next three months. I want this based off of the 24 months worth of sales I have. My sheet has sales for the last 24 months, month by month. Month Sales 1 3 2 4 3 5 4 6 5 7 6 8 7 8 8 7 9 6 10 5 11 4 12 3 13 3 14 4 15 5 16 6 17 7 18 8 19 8 20 7 21 6 22 5 23 4 24 3 25 26 27 I am trying to use the TREND function. For example if my sales were this I would expect the result for month 25 to be 3, if month 1 & 13 represented January. The result I get is 5.5 which is nothing more than the average of all 24 months. T.I.A. |
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