A random sample of 16 mid-sized cars tested for fuel consumption gave a mean of 26.4

Question

kilometers per liter with a standard deviation of 2.3 kilometers per liter.
i) Assuming that the kilometers per liter given by all mid-sized cars have a normal
distribution, find a 99% confidence interval for the population mean μ.
ii) Suppose the confidence interval obtained in (b)(i) is too wide. How can the width of this
interval be reduced? Describe all possible alternatives. Which alternative is the best and
why?

Answer 1

1. 99% = mean ± 2.575 SEm

SEm = SD/√n

2. Only thing I can think of is getting a larger sample.