PROBABILITY

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MEASURES of CENTRAL TENDENCY
$MEAN\ $
$\left(\bar{x}\right)\ $
The average of the number
$\bar{x}\ =\ \frac{\sum x}{n}$
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MEASURES of CENTRAL TENDENCY
$MEDIAN\ $
$\left(\widetilde{x}\right) $
The MIDDLE DATA,
when ARRANGE from
LEAST to GREATEST
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MEASURES of CENTRAL TENDENCY
$MODE\ $
$\left(\hat{x}\right)\ $
The VALUE that
APPEARS MOST FREQUENTLY
in a data set
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MEASURES of CENTRAL TENDENCY
$RANGE $
The DIFFERENCE between the

MAXIMUM value
to the
MINIMUM value
${\rm Value}_{max}\ -\ {\rm Value}_{min}$
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MEASURES of DISPERSION
$if\ n>30$
Population Standard Deviation
$\sigma_p=\ \sqrt{\frac{\sum\left(x-\bar{x}\right)^2}{n}}$
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MEASURES of DISPERSION
$if\ n\le\ 30$
Sample Standard Deviation
$\sigma_s=\ \sqrt{\frac{\sum\left(x-\bar{x}\right)^2}{n-1}}$
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MEASURES of POSITION (QUANTILES)
Quartiles
$Q_i=\ \frac{i}{4}\left(n\ +\ 1\right)\ $
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MEASURES of POSITION (QUANTILES)
Decile
revised figure
$D_i=\ \frac{i}{10}\left(n\ +\ 1\right)\ $
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MEASURES of POSITION (QUANTILES)
Percentile
revised figure
$P_i=\ \frac{i}{100}\left(n\ +\ 1\right)$
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DETERMINE FIRST if ARRANGEMENT is
IMPORTANT or NOT IMPORTANT
IMPORTANT = PERMUTATION

NOT IMPORTANT = COMBINATION
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PERMUTATION - arrangement is IMPORTANT

Distinct Permutation
the number of all possible
arrangements or permutations
of n distinct objects taken r at a time.
$n\ P\ r\ =\ \frac{n!}{\left(n\ -r\right)!}$
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PERMUTATION - arrangement is IMPORTANT

Repetitive Permutation
the number of all possible
arrangements or permutations
of n distinct objects taken r at a time with identical objects
$n\ P\ r\ =\ \frac{N!}{R!}$
N= number of obj. (counting certain identical obj as 1)
R= number of how many times the certain obj repeated
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PERMUTATION - arrangement is IMPORTANT

Circular Permutation
total number of ways in which n distinct objects can be arranged
around a fixed circle.
the start and end is indistinctive
$n\ P\ r\ =\ \left(n-1\right)!$
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PERMUTATION - arrangement is IMPORTANT

Circular in Space Permutation
$n\ P\ r\ =\ \frac{\left(n-1\right)!}{2}$
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COMBINATION - arrangement is NOT IMPORTANT

Distinct Combination
$n\ C\ r\ =\ \frac{n!}{r!\ \left(n-r\right)!}$
n= number of choices
r= number of outcomes
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COMBINATION - arrangement is NOT IMPORTANT

Derangement Combination
a derangement of a set leaves no element in its original place
$!n\ =n!\sum_{k=0}^{n}{\ \frac{\left(-1\right)^k}{k!}}$
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relationship between
PERMUTATION and COMBINATION
$n\ C\ r=\ \frac{n\ P\ r}{r\ !}$
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PROBABILITY
$P\ =\ \frac{SUCCESSFUL\ outcomes}{total\ number\ of\ POSSIBLE\ outcomes}$
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MATHEMATICAL EXPECTATION
If p is the probability that a person
will receive a sum of money S,
the mathematical expectation is defined

$E = pS$
p= probability of success
S= sum of prize
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ODDS in FAVOR
the likelihood of something occurring.

It is a gambling term referring to a mathematical calculation of probability.
$Odds\ in\ Favor\ =\ \frac{SUCCESSFUL\ }{failure}$
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ODDS in AGAINST or FAILURE
the likelihood of something occurring. It is a gambling term referring to a mathematical calculation of probability.
$Odds\ Against\ =\ \frac{failure\ }{SUCCESS}$
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MUTUALLY EXCLUSIVE EVENTS

Two or more events are mutually exclusive ,
they cannot occur simultaneously.
$P\left(A\ \cap B\ \right)=\ 0$
$P\left(A\ \cup B\ \right)=\ P\ \left(A\right)\ +P\ \left(B\right)$
the probability of both events happening at the same time is zero.
For example, when tossing a coin, the result can either be heads or tails, but not both
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MUTUALLY INCLUSIVE EVENTS

Two or more events are mutually inclusive,
if one or the other or both can occur.
$P\left(A\ \cap B\ \right)\neq\ 0$
$P\left(A\ \cup B\ \right)=\ P\ \left(A\right)\ +P\ \left(B\right)-P\left(A\ \cap B\ \right)$
For example, the events “buying an alarm system” and “buying bucket seats”
are mutually inclusive, as both events can happen at the same time
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CONDITIONAL PROBABILITY

Bayes Theorem
$P\left(A|B\right) \cdot P\ \left(B\right)=\ P\left(B|A\right) \cdot P\ \left(A\right)\ =P\left(A\cap B\right)$
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BINOMIAL DISTRIBUTION
In a binomial experiment
(also called the Bernoulli trial),
there are 2 mutually exclusive outcomes often referred to as “success” and “failure”, or the probability of each trial
is not affected
$ P\ \left(x\ =r\right)=\ \left(n\ C\ r\right)\cdot\left(p^r\right)\cdot{\ \left(q\right)}^{n-r}$

n =number of trials (occurrences)
r =number of successful trials
p =probability of success in a single trial
q = (1-p)
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BINOMIAL APPROXIMATION
to
NORMAL DISTRIBUTION


usually used in large value
n to be “sufficiently large” it needs to meet
the following criteria
$np\geq\ 5$
$n\left(1-p\right)\geq\ 5$
$\bar{x}\ =\ np$
$\sigma\ =\ \sqrt{npq}$
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POISSON's DISTRIBUTION

The Poisson’s probability that exactly
“r”
successes occur in a Poisson experiment
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NORMAL DISTRIBUTION

LESS than the VALUE
to the left of VALUE
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NORMAL DISTRIBUTION

in BETWEEN the 2 VALUE
towards 0
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NORMAL DISTRIBUTION

GREATER than the VALUE
to the right of VALUE
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