Suppose the probability that a randomly selected PGA Tour pl

Suppose the probability that a randomly selected PGA Tour player uses a Titleist brand golf ball is 0.65. For a sample of 9 PGA Tour players, find the probability that no less than 8 use a Titleist brand golf ball. (See exercise 33 on page 235 of your textbook for a similar problem.) Probability =

Solution

Note that P(at least x) = 1 - P(at most x - 1).          
          
Using a cumulative binomial distribution table or technology, matching          
          
n = number of trials =    9      
p = the probability of a success =    0.65      
x = our critical value of successes =    8      
          
Then the cumulative probability of P(at most x - 1) from a table/technology is          
          
P(at most   7   ) =    0.878914971

[You can type this as =BINOMDIST(7,9,0.65,1), where the last 1 is cumulative from 0 to 7.]

          
Thus, the probability of at least   8   successes is  
          
P(at least   8   ) =    0.121085029 [ANSWER]

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