Drug maker GlaxoSmithKline investigated the potential impact

Drug maker GlaxoSmith-Kline investigated the potential impact of its oral antidiabetic drug Avandia (rosiglitazone maleate) on the blood lipid levels of adult diabetics who might benefit from taking Avandia. The mean baseline LDL (low-density lipoprotein, or \"bad\" cholesterol) level for a random sample of 964 such patients was x = 125.6 milligrams per deciliter (mg/dl). The distribution of LDL levels in the adult population is known to be close to Normal with standard deviation sigma = 30 mg/dl.^10 Assuming that sigma is the same as in the general population, give a 90% confidence interval for the mean baseline LDL level mu among adult diabetics who might benefit from taking Avandia.

Solution

Confidence Interval
CI = x ± Z a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval
Mean(x)=125.6
Standard deviation( sd )=30
Sample Size(n)=964
Confidence Interval = [ 125.6 ± Z a/2 ( 30/ Sqrt ( 964) ) ]
= [ 125.6 - 1.64 * (0.966) , 125.6 + 1.64 * (0.966) ]
= [ 124.015,127.185 ]