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Question 6: A manufacturer knows that the number of items produced per hour by its two factories A and B is normally distributed with standard deviations 8.0 and 11.0 items respectively. The mean hourly amount produced by Firm A from a random sample of 50 hours is 120 units and that by Firm B from a random sample of 30 hours is 110 units. Find the 95% confidence interval for the difference in the means and comment on the estimated interval.

  • statistics -

    You will need to use a two-sample confidence interval formula.

    Here is one example:

    CI95 = (x1 − x2) ± z-value × √(s1^2/n1 + s2^2/n2)
    (Note: × means to multiply)

    x1 = mean A
    x2 = mean B

    z-value = 1.96

    s1^2 = standard deviation A (squared)
    s2^2 = standard deviation B (squared)

    n1 = sample size A
    n2 = sample size B

    Plug the values into the formula and calculate the interval.

    I hope this will help get you started.

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