Quiz3

1.

A matrix \(\Sigma\) is positive semidefinite if:

Answer

  • ☐ \( x^T\Sigma x\in\mathbb{Z}\)
  • ☐ \(x^T\Sigma x=0\)
  • ☑ xTΣ x ≥ 0
  • ☐ xTΣ x ≤ 0

2.

The probability density of the Gaussian/Normal distribution is highest at

Answer

  • ☐ \(\mu + \sigma\)
  • ☐ \(\mu - \sigma\)
  • ☑ \(\mu\)
  • ☐ \(\mu + 2\sigma\)

3.

Similarity between pairs of categorical attributes can be obtained by

Answer

  • ☐ Correlation
  • ☐ Cosine
  • ☐ Covariance
  • ☑ \(\chi^{2}\) test

4.

CLT states that when random samples are drawn from any distribution:

Answer

  • ☐ The samples are uniformly distributed
  • ☑ The means of the samples are normally distributed
  • ☐ The means of the samples are uniformly distributed
  • ☐ The samples are normally distributed

5.

An attribute A takes 2 values {yes,no}, and attribute B takes 3 values {high,medium,low}. Which of the following is not true?

Answer

  • ☐ The confusion matrix is of size 2 x 3
  • ☑ If p-value of χ2 test is 0.3 implies that A & B are independent
  • ☐ Since A & B are categorical, correlation is NOT the correct metric to measure similarity
  • ☐ The null hypothesis of χ2 test is that variables are independent