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-In [[machine learning]], [[accuracy]] refers to the ability to accurately predict the output of a given input. It is a common metric used to evaluate the performance of a [[model]] in particular [[classification]] tasks.
+==Introduction==
+In machine learning, accuracy is a metric used to evaluate the performance of a classification model. It represents the proportion of correct predictions made by the model on a set of test data, relative to the total number of predictions. Accuracy is one of the most commonly used metrics in machine learning and is often used as a benchmark for comparing the performance of different models.
-==Mathematical Definition==
+==What is Accuracy?==
-The accuracy of a model in a classification task is the sum of all the correct [[prediction]]s divided by the total number of predictions. It can be expressed mathematically as:
+Accuracy is a measure of how well a machine learning model is able to correctly predict the class labels of test data. It is defined as the ratio of the number of correct predictions made by the model to the total number of predictions made.
-Accuracy = Number correct predictions / Total number of predictions
+The formula for accuracy is:
-==Example==
+Accuracy = (Number of correct predictions) / (Total number of predictions)
-Consider a [[binary classification]] problem, where the goal is to predict whether an email is spam email or not. In a set of 1000 emails, 800 are classified as "not spam" while 200 are classified as "spam". The model makes a total of 1000 predictions during the [[evaluation phase]]. The model correctly predicted that 750 emails were "not spam" while 150 emails were "spam"; 900 total correct predictions and 100 incorrect predictions. The accuracy of the model can thus be calculated as follows:
-Accuracy = (750 + 150) / 1000 = 0.90
+For example, if a model is trained to classify images of cats and dogs and is tested on a set of 100 images, and it correctly identifies 80 of them, its accuracy is 80/100 = 0.8 or 80%.
-This means that the model accurately predicts the class of 90% percent of emails.
+==When is Accuracy Used?==
+Accuracy is a useful metric when the classes in the data set are balanced, meaning that there are roughly equal numbers of samples in each class. In such cases, accuracy provides a good measure of the overall performance of the model.
+However, when the classes are imbalanced, meaning that one class has significantly more samples than the other, accuracy can be a misleading metric. In such cases, a model can achieve a high accuracy by simply predicting the majority class, even if it performs poorly on the minority class. For imbalanced datasets, other metrics like precision, recall, and F1 score may provide a more meaningful evaluation of the model performance.
+==How is Accuracy Calculated?==
+Accuracy is calculated by comparing the predicted class labels to the true class labels of the test data. If the predicted class label matches the true class label, it is considered a correct prediction, and the count of correct predictions is incremented by one.
+Once all the predictions have been made, the count of correct predictions is divided by the total number of predictions to obtain the accuracy.
+==Factors Affecting Accuracy==
+Several factors can affect the accuracy of a classification model, including the choice of algorithm, the quality and quantity of training data, the feature selection process, and the hyperparameters used to tune the model.
+The choice of algorithm can significantly affect the accuracy of the model. Some algorithms may be better suited for certain types of data or may perform better on small or large datasets. The quality and quantity of training data can also affect the accuracy, as a model can only learn patterns that are present in the training data.
+The feature selection process is also important, as the selection of relevant features can improve the accuracy of the model. Finally, the hyperparameters used to tune the model can have a significant impact on the accuracy, and choosing the right hyperparameters can improve the performance of the model.
 ==Explain Like I'm 5 (ELI5)==
-Accuracy can be described as a score on a test. Imagine that you have to answer 10 questions. If you get 9 correct answers, your accuracy score is 9/10 or 90%. This is how [[machine learning models]] can be tested. They are given questions and then based on how many answers they got correct, we calculate their accuracy score.
+Accuracy is a way of measuring how good a computer program is at telling things apart. For example, if we want the program to tell the difference between pictures of cats and dogs, we can use accuracy to see how many pictures it gets right out of all the pictures it looks at. The higher the accuracy, the better the program is at telling cats and dogs apart.