Question

In a study of the lifespans of mattresses, a random sample of 63 mattresses were subjected to daily use. For this sample, they found that the average time (in months) before the mattress needed replacement was 16.3, and the standard deviation was 1.3. What is the upper confidence limit for a 95% confidence interval for ?μ, the mean time before mattresses need replacement?

Answer 1

n = Sample Size = 63

= Sample Mean = 16.3

s = Sample SD = 1.3

SE = s/

= 1.3/

= 0.1638

= 0.05

ndf = n - 1 = 63 - 1 = 62

From Table, critical values of t = 1.9990

The upper confidence limit for a 95% confidence interval for ?, the mean time before mattresses need replacement is given by:

16.3 + (1.9990 X 0.1638)

= 16.6274

So,

Answer is:

16.6274