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Old 07-15-2012
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Stats confidence interval for the population mean birth weight

In a health care utilization journal, results are reported from a study performed on a random sample of 100 deliveries at a large teaching hospital. The sample mean birth weight is reported as 120 ounces, and the sample standard deviation is 25 ounces. The researchers neglected to report a 95% confidence interval for the population birth weight (i.e.: mean birthweight for all deliveries in the hospital). You decide to do so, and find the 95% confidence interval for the population mean birth weight to be:

a) 119.5 ounces to 120.5 ounces
b) 115 ounces to 125 ounces
c) 70 ounces to 170 ounces
d) 117.5 ounces to 122.5 ounces
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Old 07-15-2012
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c) 70 ounces to 170 ounces
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Old 07-16-2012
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mbbs2010...how did u get C...

I thot whenever one is given the sample size ...it must be used in calculating the CI

I think its B...115 to 125
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Old 07-16-2012
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95% CI = mean +/- 2 x (SD/ sq root of n)

= 120 +/- 2 x ( 25 / sq root of 100 )

= 120 +/- 2 x 2.5 = 120 +/- 5 = 115 to 125 ounces

hope im right
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tyagee (07-16-2012)
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Old 07-16-2012
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Quote:
Originally Posted by stfidel View Post
mbbs2010...how did u get C...

I thot whenever one is given the sample size ...it must be used in calculating the CI

I think its B...115 to 125
Yup yup! U are right!
I dunno why I presumed it to be a normal distribution curve!
My bad
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Old 07-16-2012
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Quote:
Originally Posted by curiousmind View Post
95% CI = mean +/- 2 x (SD/ sq root of n)

= 120 +/- 2 x ( 25 / sq root of 100 )

= 120 +/- 2 x 2.5 = 120 +/- 5 = 115 to 125 ounces

hope im right
Thanks. Hopefully this is correct.
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