A problem on probability involving binomial distribution. A random sample of n people who walk to work are chosen, what is the probability that at least r of them are injured, given that the probability of being injured while walking to work is p.

moidu13x8

moidu13x8

Answered question

2022-09-15

A problem on probability involving binomial distribution
I'm trying to figure out the method required to solve this problem, so I stripped out the actual values to keep from getting a direct answer.
A random sample of n people who walk to work are chosen, what is the probability that at least r of them are injured, given that the probability of being injured while walking to work is p.
I don't know where to go. It feels like a binomial probability problem, but it covers a range of trials and not just one value exactly. My guess was to calculate 1 B i n o m C D F ( n , p , r 1 ). Does this seem accurate? For example, if n = 15, r = 7, p = 0.5.
I would have 1 B i n o m C D F ( 15 , 0.5 , 6 ) or
1 i = 1 6 ( 15 i ) 0.5 i ( 1 0.5 ) 15 i .

Answer & Explanation

ko1la2h1qc

ko1la2h1qc

Beginner2022-09-16Added 18 answers

Step 1
You are right, this does use the binomial distribution.
P r ( X = r ) = ( n r ) p r ( 1 p ) n r
That simply gives the probability that "r" events are true from a total of "n" possible events, with the probability of the event happening being "p"
Step 2
So using your values:
i = 7 n P r ( X = i )
= i = 7 n ( 15 i ) 0.5 i ( 1 0.5 ) 15 i

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