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[HO] CALCULATOR

Tags: #◇CSMODEL #◇Mock Exams #◇Computer Science #◇Data Science #◇Statistical Modeling #◇Python #◇Machine Learning

Calculator Guide for CSMODEL Exam

This guide covers step-by-step instructions for calculating the most common formulas on a standard scientific calculator during the CSMODEL final exam.

◇1. Association Rule Mining (Apriori)

Formulas:

  • Support(A) = Frequency(A) / Total Transactions
  • Confidence(A → B) = Frequency(A and B) / Frequency(A)
  • Lift(A → B) = Confidence(A → B) / Support(B) = Support(A and B) / [Support(A) * Support(B)]

Calculator Usage:

Calculating Lift:
Given: Confidence of A → B = 0.8, Support of B = 0.2

  1. Type 0.8
  2. Press / (divide)
  3. Type 0.2
  4. Press = (Result: 4.0)

◇2. Clustering (Euclidean Distance)

Formula:

  • Distance = √[ (x₂ - x₁)² + (y₂ - y₁)² ]

Calculator Usage:

Given: Point 1 = (1, 2), Point 2 = (4, 6)
Method 1 (Step-by-step):

  1. Calculate X difference: Type 4 - 1, press =, press the squaring key x² (Result: 9)
  2. Add Y difference: Press +, open parenthesis (, type 6 - 2, close parenthesis ), press the squaring key x², press = (Result: 25)
  3. Take the square root: Press the √ (square root) key, type 25 (or press Ans), then press = (Result: 5)

Method 2 (One-liner using parentheses):

  1. Press √
  2. Open parenthesis (
  3. Open parenthesis (, type 4 - 1, close parenthesis ), press x²
  4. Press +
  5. Open parenthesis (, type 6 - 2, close parenthesis ), press x²
  6. Close parenthesis )
  7. Press = (Result: 5)

◇3. Recommender Systems (Cosine Similarity)

Formula:

  • Cosine Similarity = (A · B) / (||A|| * ||B||)

Calculator Usage:

Given: Vector A = [3, 4], Vector B = [4, 3]

Step 1: Compute Dot Product (A · B)

  1. Type 3 * 4
  2. Press +
  3. Type 4 * 3
  4. Press = (Result: 24)
    (Write this number down: 24)

Step 2: Compute Magnitude of A (||A||)

  1. Type 3² + 4², press = (Result: 25)
  2. Press √ on the result (Result: 5)
    (Write this number down: 5)

Step 3: Compute Magnitude of B (||B||)

  1. Type 4² + 3², press = (Result: 25)
  2. Press √ on the result (Result: 5)
    (Write this number down: 5)

Step 4: Final Calculation

  1. Type 24
  2. Press /
  3. Open parenthesis (
  4. Type 5 * 5
  5. Close parenthesis )
  6. Press = (Result: 0.96)

◇4. Basic Statistics (Standard Error)

Formula:

  • Standard Error (SE) = Standard Deviation / √(Sample Size)

Calculator Usage:

Given: Standard Deviation = 12, Sample Size = 36

  1. Type 12
  2. Press /
  3. Press √ (square root), type 36
  4. Press = (Result: 2.0)

◇5. Bayesian Inference (Bayes' Theorem)

Formula:

  • P(A|B) = [ P(B|A) * P(A) ] / P(B)

Calculator Usage:

Given: P(B|A) = 0.9, P(A) = 0.01, P(B) = 0.05

  1. Type 0.9 * 0.01
  2. Press /
  3. Type 0.05
  4. Press = (Result: 0.18)

◇General Calculator Tips for the Exam:

  • Parentheses are your best friend: When dealing with fractions (like Cosine Similarity or Bayes' theorem) with multiple terms in the denominator, always wrap the denominator in parentheses. A / (B * C) is NOT the same as A / B * C.
  • Store intermediate values: For complex calculations like Cosine Similarity, write down the intermediate dot product and magnitudes on your scratch paper to avoid making a syntax error on a long one-line equation.
  • Square Roots: Depending on your calculator (Casio vs. Sharp vs. TI), you either press √ before the number, or type the number and press √ after. Make sure you know which way your specific calculator works!
  • Clear Memory: Hit AC or Clear twice before starting a completely new problem to ensure nothing is accidentally carried over from the previous calculation.

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