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Eda Formulas

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Chapter 1: DESCRIPTIVE STATISTICS

𝑹𝒂𝒏𝒈𝒆 (𝑹) = 𝑙𝑎𝑟𝑔𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒 – 𝑠𝑚𝑎𝑙𝑙𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒


𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑙𝑎𝑠𝑠𝑒𝑠 (𝒎) = 1 + 3.3 log 𝑛 ; 𝑛 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑎𝑠𝑒𝑠
R
class size (𝐜) =
m
STEM AND LEAF DISPLAY
1. Select one or more leading digits for the stem values. The remaining digits become the leaves.
2. List all the possible stem values in a vertical column.
3. Record the leaf for every observation beside the corresponding stem value.
4. Indicate the units for stems and leaves someplace in the display.
A display having between 5 and 20 stems is recommended
MEAN MEDIAN MODE VARIANCE
𝑓𝑖 𝑥𝑖 𝑛 𝑑 1 (∑ 𝑓𝑖 𝑥𝑖 )2
[ – (𝛴𝑓)𝐿 ] 𝑐 1 𝑠2 = [∑ 𝑓𝑖 𝑥𝑖2 − ]
𝒙̅=∑ ̃ = 𝐿𝑚 +
𝒙 2 ̂
𝒙 = 𝐿 𝑚𝑜 + ( ) 𝑐 𝑛 − 1 𝑛
𝑛 𝑓𝑚 𝑑 1 + 𝑑 2 ∑ 𝑓𝑖 (𝑥𝑖 − 𝑥̅ ) 2

𝑤ℎ𝑒𝑟𝑒, 𝐿_𝑚= lower class boundary of the 𝐿𝑚𝑜= lower class boundary of the 𝑆2 =
modal class 𝑛−1
𝑙𝑜𝑤𝑒𝑟 𝑙𝑖𝑚𝑖𝑡 + 𝑢𝑝𝑝𝑒𝑟 𝑙𝑖𝑚𝑖𝑡 median class
𝑥𝑖 = (𝛴𝑓)𝐿 =sum of frequencies of all 𝑑1 = excess of modal frequency of
2 STANDARD DEVIATION
classes lower than the median class the next lower class
𝑓𝑖 = 𝑐𝑙𝑎𝑠𝑠 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑑2 = excess of modal frequency of 𝑠 = √𝑠 2
𝑓_𝑚= frequency of the median class
C = size of the median class the next higher class
𝑐 = size of the modal class interval
Chapter 2: PROBABILITY
Permutation can be represented in many ways; these are as follows:
[𝑃(𝑛, 𝑘)] [𝑃𝑘𝑛 ] [nPk] [𝑃𝑛, 𝑘 ] [nPk]
1. The number of permutations of n distinct objects taken n at a time is 𝑃 = 𝑛! (𝑤𝑒 𝑠𝑎𝑦 𝑛! 𝑎𝑠 "𝑛 𝑓𝑎𝑐𝑡𝑜𝑟𝑖𝑎𝑙)
𝑛! = 𝑛(𝑛 − 1)(𝑛 − 2)(𝑛 − 3) ⋯ (2)(1)
𝑛!
2. The number of permutations of n distinct objects taken 𝑟 at a time is 𝑃 = 𝑛𝑃𝑟 = (𝑛−𝑟)!
3. The number of permutations of n objects of which 𝑛1 are identical, 𝑛2 are identical, … , 𝑛𝑚 are identical is
𝑛!
𝑃=
𝑛1 ! ∙ 𝑛2 ! ∙ ⋯ ∙ 𝑛𝑚 !

The number of combinations of n Properties of Probability


objects taken r at a time has the formula
𝑛! 𝑛𝑃𝑟
1. Positiveness 2. Certainty
𝑛
𝑛𝐶𝑟 = ( ) = = 0 ≤ P(A) ≤ 1 P(S) = 1, the probability of a sure event
𝑟 𝑟! (𝑛 − 𝑟)! 𝑟!

Additive Rules Conditional Probability


1. 𝐼𝑓 𝐴 & 𝐵 𝑎𝑟𝑒 𝑎𝑛𝑦 𝑡𝑤𝑜 𝑒𝑣𝑒𝑛𝑡, 𝑡ℎ𝑒𝑛, The conditional probability of A is given that B has
𝑷(𝑨 ∪ 𝑩) = 𝑷(𝑨) + 𝑷(𝑩) – 𝑷(𝑨 ∩ 𝑩) occurred is defined by
2. 𝐼𝑓 𝐴 & 𝐵 𝑎𝑟𝑒 𝑚𝑢𝑡𝑢𝑎𝑙𝑙𝑦 𝑒𝑥𝑐𝑙𝑢𝑠𝑖𝑣𝑒 𝑒𝑣𝑒𝑛𝑡𝑠, 𝑡ℎ𝑒𝑛 𝑨 𝑷(𝑨 ∩ 𝑩)
𝑷(𝑨 ∪ 𝑩) = 𝑷(𝑨) + 𝑷(𝑩) 𝑷 (𝑩) =
3. 𝐼𝑓 𝐴 𝑎𝑛𝑑 𝐴’ 𝑎𝑟𝑒 𝑐𝑜𝑚𝑝𝑙𝑒𝑚𝑒𝑛𝑡𝑎𝑟𝑦 𝑒𝑣𝑒𝑛𝑡𝑠, 𝑡ℎ𝑒𝑛 𝑷(𝑩)
𝑷(𝑨) + 𝑷(𝑨’) = 𝟏
𝐴𝑙𝑠𝑜, 𝑷(𝑨 ∪ 𝑩) – 𝑷(𝑨) = 𝑷(𝑩) – 𝑷(𝑨 ∩ 𝑩) = 𝑷(𝑩 ∩ 𝑨’)

Multiplicative Rule Independent Events


If the events A and B can both occur, then Two events A & B are independent if and only if
𝑨 𝑨 𝑩
𝑷 ( 𝑨 ∩ 𝑩 ) = 𝑷 ( ) · 𝑷(𝑩) 𝑷 ( ) = 𝑷(𝑨) 𝒂𝒏𝒅 𝑷 ( ) = 𝑷(𝑩)
𝑩 𝑩 𝑨
Since P (A^B) = P (B^A), then So that
𝑩 𝑷(𝑨 ∩ 𝑩) = 𝑷(𝑨) · 𝑷(𝑩)
𝑷 ( 𝑨 ∩ 𝑩 ) = 𝑷 ( ) · 𝑷(𝑨)
𝑨

Chapter 3: PROBABILITY DISTRIBUTIONS


Properties of a discrete The cumulative distribution function (cdf) The function f(x) is a probability density function (pdf) for a
probability function F(x) for a discrete random variable X is defined by continuous random variable X, defined over the set of real
1. 𝑓(𝑥) ≥ 0 𝐹(𝑥) = 𝑃 ( 𝑋 ≤ 𝑥 ) = 𝛴 𝑓(𝑢) numbers R.
2. 𝛴 𝑓(𝑥) = 1 𝑢≤𝑥 1. 𝑓(𝑥) ≥ 0

2. ∫−∞ 𝑓(𝑥)𝑑𝑥 = 1
𝑏
3. 𝑃(𝑎 < 𝑋 < 𝑏) = ∫𝑎 𝑓(𝑥)𝑑𝑥

Chapter 4: SOME DISCRETE PROBABILITY DISTRIBUTIONS


the number of success in n independent trials is The mean and variance of the binomial distribution are
𝑓(𝑥) = 𝑏 (𝑥 ; 𝑛 , 𝑝) = 𝑛 𝐶𝑥 𝑝 𝑥 𝑞 𝑛−𝑥 µ = 𝑛𝑝 𝑎𝑛𝑑 𝜎 2 = 𝑛𝑝𝑞
Poisson random variable

the number of the trial on which the kth success occurs, is given by
𝑓(𝑥) = 𝑏 ∗ (𝑥; 𝑘, 𝑝) = 𝑥−1 𝐶𝑘−1 𝑝 𝑘 𝑞 𝑥−𝑘

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