Data Science Data Science/Questions/Data Science 1

Question 1

Which of the following best describes the bias-variance tradeoff in machine learning?

Accepted Answer

A model with high bias underfits the data, while a model with high variance overfits it

Answer

Increasing model complexity always reduces both bias and variance

Answer

Bias and variance are independent properties that do not affect each other

Answer

Reducing variance always leads to higher accuracy on unseen data

Question 2

When handling missing data in a dataset, which approach is most likely to introduce bias if the data is not missing at random (MNAR)?

Accepted Answer

Listwise deletion (removing all rows with missing values)

Answer

Multiple imputation using chained equations

Answer

Mean imputation for continuous variables

Answer

Using a model that natively handles missing values

Question 3

What is the main advantage of using gradient boosting over a single decision tree?

Accepted Answer

Gradient boosting sequentially corrects the errors of prior trees, improving predictive accuracy

Answer

Gradient boosting trains faster than a single decision tree

Answer

Gradient boosting requires fewer hyperparameters to tune

Answer

Gradient boosting eliminates the need for feature scaling

Question 4

Which evaluation metric is most appropriate when the cost of false negatives is much higher than the cost of false positives, such as in cancer screening?

Accepted Answer

Recall (Sensitivity)

Answer

Accuracy

Answer

Specificity

Answer

F1 Score

Question 5

In feature selection, what does the term 'multicollinearity' refer to and why is it a problem in linear regression?

Accepted Answer

When independent features are highly correlated with each other, making coefficient estimates unreliable

Answer

When two target variables are highly correlated, causing prediction instability

Answer

When a feature has too many missing values to be useful in a model

Answer

When the target variable has a non-linear relationship with the features

Question 6

Which statistical test is most appropriate for determining whether two independent groups have significantly different means, assuming normally distributed data and unknown but equal variances?

Accepted Answer

Independent samples t-test (Student's t-test)

Answer

Chi-square test

Answer

Paired t-test

Answer

Mann-Whitney U test