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Uncertainty in Multiclass Classification

Dr. Rishabh Pathak
1. What is Uncertainty in Classification? Uncertainty refers to the model’s confidence or doubt in its predictions. Quantifying uncertainty is important to understand how reliable each prediction is. In multiclass classification , uncertainty estimates provide probabilities over multiple classes, reflecting how sure the model is about each possible class. 2. Methods to Estimate Uncertainty in Multiclass Classification Most multiclass classifiers provide methods such as: predict_proba: Returns a probability distribution across all classes. decision_function: Returns scores or margins for each class (sometimes called raw or uncalibrated confidence scores). The probability distribution from predict_proba captures the uncertainty by assigning a probability to each class. 3. Shape and Interpretation of predict_proba in Multiclass Output shape: (n_samples, n_classes) Each row corresponds to the probabilities of ...
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Stratified Sampling

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Dr. Rishabh Pathak

Stratified sampling is a sampling technique in which the population is divided into subgroups or strata based on certain characteristics that are relevant to the research objectives. Samples are then randomly selected from each stratum to ensure representation of the diversity within the population. Here are some key points about stratified sampling:

1.    Process:

o    In stratified sampling, the population is first divided into mutually exclusive and homogeneous subgroups called strata. These strata are based on specific characteristics such as age, gender, income level, or geographic location.

o    Random samples are then drawn from each stratum in proportion to the population size of the stratum. This ensures that each stratum is adequately represented in the final sample.

2.    Purpose:

o    The primary purpose of using stratified sampling is to ensure that all subgroups within the population are represented in the sample. By dividing the population into strata, researchers can capture the variability within different segments of the population and obtain more precise estimates for each subgroup.

3.    Advantages:

o    Provides more accurate and reliable estimates for each stratum by ensuring adequate representation.

o    Allows for comparisons between different subgroups within the population.

o    Helps in reducing sampling variability and increasing the efficiency of the sampling process.

4.    Disadvantages:

o    Requires prior knowledge of the population characteristics to define appropriate strata.

o    Can be more complex and time-consuming compared to simple random sampling or other sampling methods.

o    If the population characteristics change over time, the defined strata may become outdated and lead to biased results.

5.    Types:

o    There are two main types of stratified sampling:

§  Proportional stratified sampling: Where the sample size from each stratum is proportional to the population size of that stratum.

§  Disproportional (or quota) stratified sampling: Where the sample size from each stratum is not proportional to the population size, but rather based on specific research considerations.

6.    Applications:

o    Stratified sampling is commonly used in market research, opinion polls, social sciences, and medical research. It is particularly useful when the population exhibits significant diversity or when researchers want to ensure representation from different subgroups.

7.    Considerations:

o    When using stratified sampling, researchers should carefully define the strata based on relevant characteristics and ensure that the sampling process within each stratum is random. It is important to maintain the independence of samples from different strata to avoid bias.

Stratified sampling is a valuable sampling technique that allows researchers to obtain more accurate and detailed insights by considering the diversity within the population. By stratifying the population based on relevant characteristics and sampling from each stratum, researchers can enhance the precision and reliability of their study results.

 

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