Step 1 :The problem is asking for the percentage of times the machine will dispense more than 7.3 oz of coffee. This is a problem of normal distribution. We know that the mean is 7.8 oz, the standard deviation is 0.2 oz, and we want to find the probability of getting more than 7.3 oz.
Step 2 :To solve this, we need to convert the value 7.3 oz to a z-score, which is a measure of how many standard deviations an element is from the mean. The formula for the z-score is: \(z = \frac{X - \mu}{\sigma}\) where X is the value we are interested in (7.3 oz), \(\mu\) is the mean (7.8 oz), and \(\sigma\) is the standard deviation (0.2 oz).
Step 3 :Let's calculate the z-score first. Using the values X = 7.3, \(\mu\) = 7.8, and \(\sigma\) = 0.2, we find that \(z = -2.5\). This means that 7.3 oz is 2.5 standard deviations below the mean.
Step 4 :Now we need to find the probability associated with this z-score. However, the standard normal distribution table usually gives the probability for less than a certain z-score, and we want the probability for more than a certain z-score. So we need to subtract the probability we find from 1 to get the correct answer.
Step 5 :The probability associated with a z-score of -2.5 is approximately 0.9938. This means that approximately 99.38% of the time, the machine will dispense more than 7.3 oz of coffee.
Step 6 :Final Answer: \(\boxed{99.38\%}\) of the time the machine will dispense more than 7.3 oz.