1.The mean weight of 15 randomly selected newborn babies at a local hospital is 7.62 lbs and the standard deviation is 1 lbs. Assume the weight of newborn babies has approximately normal distribution.

(a) Find the margin of error for the 90% confidence interval for the mean weight of all newborn babies at this hospital. (Round your answer to two decimal places.)

(b) Use information from part (a) to fill in the banks in the following sentence: % of all samples of size have sample means within lbs of the population mean.

(c) Find a 90% confidence interval for the mean weight of all newborn babies at this hospital. (Round your answer to two decimal places.)

lbs<< lbs

(d) If you increase the confidence level (1), will the confidence interval estimate be wider or narrower? Explain.

2.At the Foremost State Bank the average savings account balance in 2012 was $1650. A random sample of 41 savings account balanes for 2013 yielded a mean of $1900 with a standard deviation of $125. At the=0.10 significance level test the claim that the mean savings account balance in 2013 is different from the mean savings account balance in 2012.

(a) Identify the correct alternative hypothesis.

• >$1650
• =$1650
• $1650
• <$1650

(b) The test statistic value is . (Round your answer to two decimal places.)

(c) Using the critical value approach (traditional method), the critical value is . (Round your answer to three decimal places.)

(d) Based on your answers above, do you

• Fail to reject theH0
• Reject theH0

(e) Explain your decision about the claim.

3.If n=27,(x-bar)=46, and s=18, construct a confidence interval at a 95% confidence level. Assume the data came from a normally distributed population.

Give your answers to one decimal place.

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