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A coffee machine is supposed to dispense 200 ml of coffee per cup. However, the amount varies slightly from cup to cup.
Let \(X_i\) be the volume of a single cup. Based on quality control, the volume has a mean \(\mu = 200\) ml and a standard deviation \(\sigma = 15\) ml.
A health inspector takes a random sample of 50 cups. Let \(\overline{X}_{50}\) be the average volume of these 50 cups.
  1. Find the expected value of the sample mean, \(E(\overline{X}_{50})\).
  2. Calculate the standard deviation for a single cup (\(\sigma\)), and then find the standard deviation of the sample mean, \(\sigma(\overline{X}_{50})\).
  3. The distribution of a single cup is not necessarily normal. Can we assume the sample mean \(\overline{X}_{50}\) is normally distributed? Explain.
  4. Find the probability that the average volume of the sample is less than 195 ml.

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