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To estimate the average weight of air-freight packages a sample of size 400 was collected. The...

  1. To estimate the average weight of air-freight packages a sample of size 400 was collected. The sample mean for these 400 packages was found to be 85.6 and the sample standard deviation was 3.2.
  1. Construct a 95% confidence interval for the average weight of air-freight packages.
  2. Find the minimum required sample size for estimating the mean of a population to within 0.4 with 98% confidence.
  3. If you test the hypotheses Ho : μ = 80 versus H1 : μ  80, what kind of decision will you make if α = 0.05?
  4. Did you make a Type I or Type II error if the actual value μ = 82?

Math   Statistics-And-Probability   
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To calculate the confidence interval we will use z distribution.

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