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Binomial and Geometric Distributions Delta On-Time Performance at Hartsfield- Jackson Atlanta International (June, 2003 - June, 2015) http://www.transtats.bts.gov/OT_Delay/ot_delaycause1.asp?display=data&pn=1
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Data / Model Total Operations: 2,278,897 On-Time Operations: 1,824,432 Proportion On-Time: 1824432/2278897 =.8006 (.80) Will consider random samples of various sizes from this population of operations Y ≡ # of On-Time operations out of the sample of n Y ~ Binomial(n, p Y = 0.80) X ≡ # of Flights sampled until the first NOT On-Time Arrival is selected X ~ Geometric(p X = 0.20)
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Binomial Distribution – Probability Function
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Geometric Distribution Used to model the number of Bernoulli trials needed until the first Success occurs (P(S)=p) First Success on Trial 1 S, y = 1 p(1)=p First Success on Trial 2 FS, y = 2 p(2)=(1-p)p First Success on Trial k F…FS, y = k p(k)=(1-p) k-1 p
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Binomial Distribution – Expected Value
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Geometric Distribution – Expected Value
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Binomial Distribution – Variance and SD
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Geometric Distribution – Variance and SD
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Binomial Distribution for On-Time Flights
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Binomial Distributions for n=1,2,3,4,10,25 In EXCEL: Create a column of values 0,1,2,…,n (Say 0 is in cell A2) In Cell B2, Type: =BINOM.DIST(A2,n,p,0) Copy and paste that cell alongside 1 (A3),…,n Note that the 0 at the end gives P(Y = y) = p(y) If you use 1 instead, you get P(Y ≤ y) = F(y)
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Several Binomial Distributions with p=0.8
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Geometric Distribution Probabilities
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Geometric Distribution In EXCEL: Create a column of values 1,2,…,Y* for some large value of Y* (Say 1 is in cell A2) In Cell B2, Type: =NEGBINOM.DIST(A2-1,1,p,0) Copy and paste that cell alongside 1 (A3),…,Y* Note that the 0 at the end gives P(Y = y) = p(y) If you use 1 instead, you get P(Y ≤ y) = F(y)
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Geometric Distribution Probabilities and CDF
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Moment-Generating Function
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Moment-Generating Function – Binomial Distribution
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Geometric Distribution – MGF
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Probability-Generating Functions
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Probability-Generating Functions - Binomial
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Geometric Distribution – PGF
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