A random sample of the birth wieghts of 186 babies has a mean of 3103 g and a st

Question

A random sample of the birth wieghts of 186 babies has a mean of 3103 g and a standard deviation of 696 g. These babies were born to mothers who did not use cocaine during their pregnancies.

What is the best point estimate of the mean wight of babies born to mothers who did not use cocaine during their pregnancies?

Constuct a 95% confidence interale stimate of the mean birth wieght for all such babies.

Compare the confidence interval from part b to this to this confidence interval obtained from birth wights of babies born to mothers whoused cocaine during prgnancy: 2608 < µ < 2792g. Does cocain use appear to affect the birth weight of a baby?

Explanation / Answer

sample size, n = 186 mean , µ = 3103 g standard deviation , s = 696 g. standard error, e = s / vn = 696 /v186 = 51.03 These babies were born to mothers who did not use cocaine during their pregnancies.

the best point estimate of the mean wight of babies born to mothers who did not use cocaine during their pregnancies = µ = 3103 g

at 95% confidence for a two tail distribution , z = 1.96 (from z table) 95% confidence interale stimate of the mean birth wieght for all such babies =µ ± (z*e) =3103 ± (1.96*51.03) =(3002.9812, 3203.0188)

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