Excel and Google Sheets are powerful tools used in data analysis and forecasting. Today, we will discuss in detail the FORECAST.ETS.CONFINT function, known as TAHMİN.ETS.GVNARAL in Turkish versions. This function is particularly useful for making predictions at a specified confidence interval for a future point, especially when working with time series data.

Forecast Model and Syntax

The FORECAST.ETS.CONFINT function allows for the prediction of a future value within a specified confidence interval based on a given time series. The syntax for this function in Excel and Google Sheets is as follows:

 TAHMİN.ETS.GVNARAL(hedef_tarih, değerler, zamanlar, [güven_aralığı], [sezonluk], [veri_uzunluğu], [eksik], [agregat], [dönem_konumu]) 

• hedef_tarih: The date or time for which the prediction is to be made.
• değerler: The independent dataset of time series data.
• zamanlar: The dependent dataset of time series data, typically includes dates or time intervals.
• güven_aralığı (optional): The confidence interval ratio used to determine the prediction’s accuracy, defaults to 0.95 (95%).
• sezonluk (optional): Indicates the seasonality of the dataset (“None”, “Automatic”, or a specific number of seasonal periods), with “Automatic” as the default.
• veri_uzunluğu (optional): Specifies the number of past points upon which the forecast model will be based.
• eksik (optional): The value to substitute for missing data, with automatic estimation as the default.
• agregat (optional): Function that denotes how multiple values will be processed.
• dönem_konumu (optional): Specifies the starting position of the period in the forecast model.

Practical Applications and Solution Examples

Example 1: Sales Forecasting

ABC Company wants to forecast sales for the next month using sales data from the past 12 months. The data is recorded on the last day of each month.

Step 1: Organize the data into a table format.

 Zaman | Satış -----------|------ 01.01.2023 | 200 01.02.2023 | 220 01.03.2023 | 210 ... 01.12.2023 | 240  

Step 2: Apply the forecast function.

 =TAHMİN.ETS.GVNARAL("01.01.2024", B2:B13, A2:A13) 

This formula will calculate the sales forecast for 01.01.2024, as well as providing the uncertainty interval.

Example 2: Stock Level Forecasting

A retail store wants to predict product stock levels for the next 6 months using bi-monthly stock level data for the past 2 years.

Step 1: Arrange the relevant data in a table format.

 Zaman | Stok -----------|------ 01.01.2021 | 1500 01.02.2021 | 1580 01.03.2021 | 1620 ... 01.12.2022 | 1800  

Step 2: Execute the forecast.

 =TAHMİN.ETS.GVNARAL("01.07.2023", B2:B25, A2:A25) 

This formula will provide a stock level forecast for 01.07.2023 and the corresponding confidence interval.

This function enables businesses to make more accurate planning for future periods. Forecasting plays a significant role in resource management and budgeting processes.

Daha fazla bilgi: https://support.microsoft.com/tr-tr/office/tahmin-işlevleri-başvuru-897a2fe9-6595-4680-a0b0-93e0308d5f6e#_forecast.ets.confint