Step 1 :First, we need to calculate the probability of success, which is the number of times Ron was hit by a pitch divided by the number of plate appearances. This gives us \( p = \frac{21}{602} = 0.03488372093023256 \).
Step 2 :Next, we use the binomial probability formula to find the probability of exactly one success in 23 trials. The formula is \( P(X=k) = C(n, k) \cdot p^k \cdot (1-p)^{n-k} \), where \( n \) is the number of trials, \( k \) is the number of successes, \( p \) is the probability of success, and \( C(n, k) \) is the number of combinations of \( n \) items taken \( k \) at a time.
Step 3 :Substituting the given values into the formula, we get \( P(X=1) = C(23, 1) \cdot (0.03488372093023256)^1 \cdot (1-0.03488372093023256)^{23-1} \).
Step 4 :Calculating the above expression, we find that the probability that Ron will get hit by a pitch exactly once in the first playoff series is approximately 0.367.
Step 5 :Rounding to three decimal places, the final answer is \(\boxed{0.367}\).