Question

A new kind of typhoid shot is being developed by a medical research team. The old typhoid shot was known to protect the population for a mean time of 36 months, with a standard deviation of 3 months. To test the time variability of the new shot, a random sample of 23 people were given the new shot. Regular blood tests showed that the sample standard deviation of protection times was 1.7 months. Using a 0.05 level of significance, test the claim that the new typhoid shot has a smaller variance of protection times. (f) Find a 90% confidence interval for the population standard deviation. (Round your answers to two decimal places.) lower limit upper limit How do i get the lower and upper numbers?

Answer 1

n = Sample Size = 23

s = Sample Standard Deviation =1.7

= 0.10

Confidence Interval is given by:

Degrees of freedom = n - 1 16 - 1 = 15

Low side

From Table:

Low Side:

High side:

From Table:

High side:

So,

Confidence Interval:

1.32 < < 2.44

So,

Lower number = 1.32

Upper number = 2.44