Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A netball player scores from a free shot with probability , independently each time. She takes shots. Find the probability that she scores exactly times. Find the probability that she scores every time. Find the mean number of goals. Give the probabilities to four decimal places.
For independent trials with success probability and , , with mean and variance . Check the four conditions first: fixed , two outcomes, the same , independent trials.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The model. , because the shots are independent with the same probability.
Step 2. Exactly four. .
Step 3. All six. .
Step 4. The mean. .
Answer: , and .
Check. The mean is , so the most likely counts are and , and a count of having probability about is reasonable.
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