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영) 기초 statstics(R프로그램 이용) - 5

저작시기 2011.06 |등록일 2016.01.02 | 최종수정일 2016.01.18 워드파일MS 워드 (doc) | 11페이지 | 가격 300원

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해외에서 1학년 때 배운 기초 statstics 문제입니다. R프로그램 이용

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Assignment Five; twenty percent of course mark

Specimen answers. Note: some answers have a commentary starting “The A+ student ...”. These parts are not required for full credit, but are included to illustrate statistical thinking

Questions
1. In a binomial distribution with n = 10 trials and p = 0.3 of success, what is the probability of observing exactly 3 successes? (give a numerical value and R idiom, or mathematical expression) (15 marks)

answer: any of

> dbinom(3,10,0.3)
[1] 0.2668279
> choose(10,3)*0.3^3*0.7^7
[1] 0.2668279
> factorial(10)/(factorial(3)*factorial(7))*0.3^3*0.7^7
[1] 0.2668279
>

[the A+ student checks this:

> table(rbinom(1e6,10,0.3)==3)

FALSE TRUE
733356 266644
>

Which is close to the theoretical value of 266827.9
]

2. In a physics experiment, a radioactive source is placed for a _xed amount of time, next to a Geiger counter that detects nuclear decay. The counter records how many decay events (\counts") occur during the experiment.

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