← Quant playground

Free practice library

Interview practice

Solve complete questions with progressive hints, worked solutions and Python implementations. Each question explains its assumptions and source match. Original interpretations are labelled explicitly.

752

Ready to practise

174

Not yet playable

926

Catalogue titles

Public standard problems and original exercises; hidden Trading Interview questions have not been verified.

174 titles have been investigated but remain unresolved. Their missing details are recorded without adding substitute exercises. Every playable question has a guided animated answer; selected questions also have custom diagrams.

Practise Learnr’s own questions →Follow a role-specific curriculum →

752 matching entries · page 1 of 16

Linear Algebra · Easy

Ordinary Least Squares (OLD) Method

Original interpretation · Match confidence: medium

Company use unverified
About this question’s source match

The catalogue says Ordinary Least Squares (OLD) Method; the expanded words identify OLS and OLD is treated as a label typo, without claiming the hidden numerical statement. The hidden Trading Interview wording, parameters and requested subparts have not been verified.

Fit an ordinary least-squares line y≈a+bt to observations(t,y)=(0,1),(1,2),(2,2). Find a,b, fitted values, residuals and residual sum of squares. Verify residual orthogonality to both design columns.

Assumptions and constraints

  • Use exact arithmetic until the final numerical approximation.
  • Answer every requested subpart and justify your reasoning.

Examples

y=(1,2,3) at t=(0,1,2)
→ a1,b1,RSS0

Data are already on a line.

Company evidence · unverified

No company-specific source has been matched to this exercise. Its references support the topic or solution method; they do not establish employer use.

References

Read the supporting material without leaving your question.

Catalogue metadata captured 2026-10-12. Metadata source.