Question 494598: Two growth hormones are being considered. A random sample of 10 rats was given the first hormone and their average weight gain was x1 = 2.3 pounds with standard deviation s1 = 4 pound. For the second hormone, a random sample of 15 rats had an average weight gain of x2 = 1.9 pounds with standard deviation s2 = 0.2 pound. Assume the weight gains follow a normal distribution. Find a 90% confidence interval for the difference in average weight gain for the two growth hormones.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Two growth hormones are being considered. A random sample of 10 rats was given the first hormone and their average weight gain was x1 = 2.3 pounds with standard deviation s1 = 4 pound. For the second hormone, a random sample of 15 rats had an average weight gain of x2 = 1.9 pounds with standard deviation s2 = 0.2 pound. Assume the weight gains follow a normal distribution. Find a 90% confidence interval for the difference in average weight gain for the two growth hormones.
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I worked out your problem without the calculator.
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x-bar: 2.3-1.9 = 0.4
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ME: 1.645*sqrt[(4^2/10) + (0.2^2/15)] = 2.08
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90%CI: 0.4-2.08 < u1-u2 < 0.4+2.08
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90%CI: -1.68 < u1-u2 < 2.48
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Cheers,
Stan H.
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A. 0.20 to 0.60 pounds
B. 0.17 to 0.63 pounds
C. 0.15 to 0.65 pounds
D. 0.24 to 0.56 pounds
I ran a 2-Sample T Interval TI-84 program and
got the following interval:
(-1.92,2.72)
df = 9.03
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A 2-Sample Z Interval gives the following interval:
(-1.68,2.48)
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If I were you I would doubt the "answer" choices
you were given.
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Cheers,
stan H.
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