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# Prediction Accuracy And Error Measures

## Contents

In Praise of Simple Models ► October (6) ► 2005 (6) ► June (1) ► May (1) ► April (1) ► March (1) ► February (1) ► January (1) ► 2004 The most popular of these the information theoretic techniques is Akaike's Information Criteria (AIC). It is helpful to illustrate this fact with an equation. How wrong they are and how much this skews results varies on a case by case basis. weblink

The actual values for the period 2006-2008 are also shown. The Chaid approach to segmentation modeling: Chi-squared automatic interaction detection. The standard procedure in this case is to report your error using the holdout set, and then train a final model using all your data. That is, it fails to decrease the prediction accuracy as much as is required with the addition of added complexity.

## Prediction Error Definition

Select the observation at time $k+i$ for the test set, and use the observations at times $1,2,\dots,k+i-1$ to estimate the forecasting model. Long-range Forecasting: From Crystal Ball to Computer. Morgan Kaufman, 1991.  S. Given a parametric model, we can define the likelihood of a set of data and parameters as the, colloquially, the probability of observing the data given the parameters 4.

1. Part of Springer Nature.
2. Why Overfitting is More Dangerous than Just Poor Accuracy, Part II In Part I, Iexplained one problem with overfitting the data: estimates of the target variable in regions without any training
3. R2 is an easy to understand error measure that is in principle generalizable across all regression models.
4. of the accuracies obtained  Cross-validation (k-fold, where k = 10 is most popular)  Randomly partition the data into k mutually exclusive subsets, each approximately equal size  At i-th
5. Cameron-Jones.
6. For each fold you will have to train a new model, so if this process is slow, it might be prudent to use a small number of folds.

Sometimes, different accuracy measures will lead to different results as to which forecast method is best. Data Mining and Knowledge Discovery, 2(2): 121-168, 1998  P. KDD'95  H. Prediction Accuracy Measure It is defined by $$\text{sMAPE} = \text{mean}\left(200|y_{i} - \hat{y}_{i}|/(y_{i}+\hat{y}_{i})\right).$$ However, if $y_{i}$ is close to zero, $\hat{y}_{i}$ is also likely to be close to zero.

Information theoretic approaches assume a parametric model. CPAR: Classification based on predictive association rules. Cohen. If you randomly chose a number between 0 and 1, the change that you draw the number 0.724027299329434...

Australasian Journal of Information Systems 5(1): 30–44.CrossRefGoogle ScholarLokan C. (2005). Prediction Error Psychology Hence Similarly, ) 5 14 age pi ni I(pi, ni) <=30 2 3 0.971 31…40 4 0 0 >40 3 2 0.971 (3,2) 0.694 14 (4,0) 14 14 + = = This procedure is sometimes known as a "rolling forecasting origin" because the "origin" ($k+i-1$) at which the forecast is based rolls forward in time. At these high levels of complexity, the additional complexity we are adding helps us fit our training data, but it causes the model to do a worse job of predicting new

## Prediction Error Statistics

IEEE Transactions on Software Engineering 29(11): 985–995.CrossRefGoogle ScholarGneiting T (2011). http://www.slideshare.net/salahecom/08-classbasic A. Prediction Error Definition in each fold is approx. Prediction Error Formula with my very small experince wodatamining involving regression problems.

ECML’93.  J. http://fapel.org/prediction-error/prediction-error-regression.php Journal of Systems and Software 27(1): 3–16.CrossRefGoogle ScholarMyrtveit I and Stensrud E (2012). Bagging, boosting, and c4.5. Quinlan. Prediction Error Regression

Generated Mon, 24 Oct 2016 08:24:59 GMT by s_nt6 (squid/3.5.20) ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: http://0.0.0.10/ Connection Han. Method to estimate parameter values in software prediction models. check over here Classification: Basic Concepts  Classification: Basic Concepts  Decision Tree Induction  Bayes Classification Methods  Rule-Based Classification  Model Evaluation and Selection  Techniques to Improve Classification Accuracy: Ensemble Methods

Chapman & Hall, 1990.  G. Prediction Error Calculator So I agree with you on R^2, but conditionally, and in most of, but not all of, the modeling I do, I prefer using another metric. 6:35 AM Post a Comment Unsupervised Learning  Supervised learning (classification)  Supervision: The training data (observations, measurements, etc.) are accompanied by labels indicating the class of the observations  New data is classified based on

## doi:10.1057/jors.2014.103AbstractSurveys show that the mean absolute percentage error (MAPE) is the most widely used measure of prediction accuracy in businesses and organizations.

Random Forest (Breiman 2001)  Random Forest:  Each classifier in the ensemble is a decision tree classifier and is generated using a random selection of attributes at each node to This is a much more efficient use of the available data, as you only omit one observation at each step. The following points should be noted. How To Calculate Prediction Error In this region the model training algorithm is focusing on precisely matching random chance variability in the training set that is not present in the actual population.

Tan, A. We can then compare different models and differing model complexities using information theoretic approaches to attempt to determine the model that is closest to the true model accounting for the optimism. Bagging: Boostrap Aggregation  Analogy: Diagnosis based on multiple doctors’ majority vote  Training  Given a set D of d tuples, at each iteration i, a training set Di of this content In our illustrative example above with 50 parameters and 100 observations, we would expect an R2 of 50/100 or 0.5.