A new drug is introduced that is supposed to reduce fevers. Tests are done with the
drug. The drug is given to 70 people who have fevers. It is found that the mean time
that it takes for the fever to get back to normal for this test group is 400 minutes with
a standard deviation of 85 minutes. Find the 95% confidence interval for the mean time
that the drug will take to reduce all fevers for all people.
The drug will ultimately sold to a very large number of people. So, we may assume a
very large population. Since the sample size is greater than 30, we should use Case 1:
Very large population and very large sample size.
We are given the sample mean and sample standard deviation. So, we have
n=70 x =400 s=85
We will use these values in the equation:
For an 95% confidence level, we look at table 6.1 and find that z = 1.96. When we
substitute these values into our equation, we get:
When we do the arithmetic on the right and left hand side, we get:
380.09 < μ< 419.91.
A certain school has 200 male students. The school nurse would like to know how many
calories the male students consume per day. So, she samples 60 male students and
, finds that the mean calorie consumption of the 60 is 2230 calories per day with a
standard deviation of 190 calories per day.
Find the 95 % confidence interval for mean calorie intake of all the male students in the
school.