Knowledge Flashcards

Which probability distribution is most appropriate for modeling the number of events occurring in a fixed time interval?

Answer: Poisson distribution

The Poisson distribution models the count of independent events occurring in a fixed interval of time or space.

What does the term 'bias-variance tradeoff' describe in machine learning?

Answer: The tension between underfitting (high bias) and overfitting (high variance)

Bias-variance tradeoff refers to the tension between a model's error due to oversimplification (bias) and its sensitivity to training data fluctuations (variance).

In SQL, what does a LEFT JOIN return?

Answer: All rows from the left table and matching rows from the right

A LEFT JOIN returns all rows from the left table and the matched rows from the right table; unmatched right-table rows appear as NULL.

What is the purpose of cross-validation in model evaluation?

Answer: To estimate model performance on unseen data using multiple train/test splits

Cross-validation repeatedly splits data into training and validation sets to produce a more reliable estimate of generalization performance.

Which measure of central tendency is most resistant to outliers?

Answer: Median

The median is resistant to outliers because it depends only on the middle value(s), not the magnitude of extreme values.

What does PCA (Principal Component Analysis) primarily accomplish?

Answer: Reduces dimensionality by projecting data onto directions of maximum variance

PCA transforms features into a smaller set of uncorrelated principal components that capture the most variance in the data.

In the context of hypothesis testing, what does a p-value represent?

Answer: The probability of observing results at least as extreme as those seen, assuming the null hypothesis is true

The p-value is the probability of obtaining a test statistic as extreme or more extreme than observed, under the assumption that the null hypothesis is true.