Skip to content
START WITH A QUESTION

What would you like to understand?

Find an answer. See the moment it becomes clear. Follow the idea further.

← Concept directory

Answers for “平滑常数 alpha 代表什么?”

9 keyword matches

Understanding your question. You can explore the search results below now.

Meet the concept

↗

The smoothing constant alpha (α\alpha) is a parameter that determines the weights assigned to observations in exponential smoothing. It controls how much priority or weight is given to the most recent actual data versus the historical forecast, with newer data receiving higher priority.

Conditions: α\alpha is a smoothing parameter or constant.; It is used in time series forecasting to assign exponentially decreasing weights to past observations.; The domain of α\alpha is typically 0≤α≤10 \le \alpha \le 1.

Meet the concept

↗

The video presents the exponential smoothing forecast formula as a weighted average of the current actual demand and the current forecast. The next period's forecast is calculated by multiplying the current actual demand by the smoothing constant α\alpha and adding the product of the previous forecast and the complementary weight (1−α)(1-\alpha).

Conditions: The formula is used to compute the forecast for period t+1t+1.; The same smoothing constant α\alpha is used throughout the worked example.; The initial forecast F1F_1 must be specified before recursion can begin.

Find a method

↗

The Year 3 forecast is calculated by applying the exponential smoothing formula to the Year 2 actual demand and the Year 2 forecast. The actual demand of 365 is weighted by α=0.4\alpha=0.4, and the previous forecast of 310 is weighted by (1−α)=0.6(1-\alpha)=0.6, yielding a new forecast of 332.

Conditions: The smoothing constant α\alpha is 0.4.; The actual demand for Year 2 (A2A_2) is 365.; The forecast for Year 2 (F2F_2) is 310.

Meet the concept

↗

In this forecasting method, α\alpha is the smoothing constant that determines the weight assigned to the most recent actual demand. The term (1−α)(1-\alpha) is the complementary weight applied to the previous forecast.

Conditions: α\alpha is fixed at 0.4 in the worked example.; (1−α)(1-\alpha) is calculated as 0.6.; The weights must sum to 1 for the formula to represent a valid weighted average.

Meet the concept

↗

Alpha is defined in the video as the exponential smoothing constant. It multiplies the previous forecast error and determines the size of the adjustment added to the previous forecast.

Conditions: Treated as a given constant in the problem.; Held fixed across all periods in the example.

Understand why

↗

The Year 2 forecast is 310 because both the actual demand for Year 1 and the initialized forecast for Year 1 are exactly 310. When a weighted average is calculated using two identical values, the result is that same value, regardless of the weights used.

Conditions: The smoothing constant α\alpha is fixed at 0.4.; The actual demand for Year 1 (A1A_1) is 310.; The initialized forecast for Year 1 (F1F_1) is 310.

Find a method

↗

To calculate exponential smoothing forecasts step-by-step, first initialize the first forecast equal to the first actual demand. Then, for each subsequent period, substitute the previous period's actual demand and previous forecast into the formula Ft+1=αAt+(1−α)FtF_{t+1} = \alpha A_t + (1-\alpha)F_t to compute the next forecast, repeating this recursive process until the target period is reached.

Conditions: The smoothing constant α\alpha is fixed across all periods.; An initial forecast F1F_1 is established from A1A_1.; Each new forecast depends only on the immediately preceding actual demand and forecast.

Meet the concept

↗

The video presents the single-parameter exponential smoothing update rule. The new forecast equals the prior forecast plus a fraction alpha of the prior forecast error, where the error is measured as actual minus forecast from the previous period.

Conditions: Used recursively over discrete time periods.; Requires a starting forecast value.; In the example, alpha is supplied as 0.2.

Find a method

↗

The video translates the mathematical recurrence into an Excel formula. For Week 2, the current forecast is computed from the Week 1 forecast in C4, the Week 1 actual in B4, and the smoothing constant in B2.

Conditions: Requires a table with actuals in one column and forecasts in another.; Uses relative references for prior row values and an absolute reference for alpha.