Assume that the GRE subject scores are normally distributed with mean 100 and st

Question

Assume that the GRE subject scores are normally distributed with mean 100 and standard deviation 25. Answer the following questions: What is the probability that the average grade for any 36 applicants exceeds 94? If only the top 10% students are eligible to apply for Ph.D. degree, what is the minimum grade that is eligible to apply for Ph.D.? When people smoke, they absorb is converted to cotinine, which can be measured. A sample of 40 smokers has a mean cotinine level of 174.0 ml. Assuming that sigma = 119.5 ng ml. Construct a 99% confidence interval for the actual mean of the cotinine level.

Explanation / Answer

here mean =174

and standard error =std deviation/(n)1/2 where n=40

=18.8946

for 99%; z =2.5758

hence confidence interval =mean +/- z*std error =(125.3307 ;222.6693)

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