FORMULA CHAPTER
Chapter 26 – Statistics
Arithmetic Mean of Ungrouped Data
Worked example
Given: 2, 4, 6 Calculation: x̄ = 12/3 Answer: x̄ = 4.
Arithmetic Mean of Grouped Data
Worked example
Given: x = 2,4; f = 3,2 Calculation: x̄ = (3×2+2×4)/5 Answer: x̄ = 2.8.
Mean by Direct Method
Worked example
Given: class marks 5,15; frequencies 2,3 Calculation: x̄ = (2×5+3×15)/5 Answer: x̄ = 11.
Mean by Assumed Mean Method
Worked example
Given: A = 20, Σfd = 30, Σf = 10 Calculation: x̄ = 20 + 30/10 Answer: x̄ = 23.
Mean by Step-Deviation Method
Worked example
Given: A = 20, h = 10, Σfu = 3, Σf = 6 Calculation: x̄ = 20 + (3/6)10 Answer: x̄ = 25.
Median of Ungrouped Data
Worked example
Given: 2, 5, 8, 10 Calculation: Median = (5 + 8)/2 Answer: Median = 6.5.
Median of Grouped Discrete Data
Worked example
Given: N = 9 Calculation: Median position = (9+1)/2 = 5th item Answer: Read the variate containing the 5th item.
Median of Grouped Continuous Data
Worked example
Given: l=20, N=50, F=18, fₘ=14, i=10 Calculation: Median = 20 + [(25−18)/14]10 Answer: Median = 25.
Mode of Grouped Data
Worked example
Given: l=20, fₘ=12, fₘ₋₁=8, fₘ₊₁=10, i=10 Calculation: Mode = 20 + (4/6)10 Answer: Mode ≈ 26.67.