a. 99% = mean ± Z SEm
SEm = SD/√n
find the table in the back of your text labeled "areas under normal distribution to find the proportion (±.005) and its Z score. Insert into equation above and calculate.
b. One is increase sample size.
A random sample of 16 mid-sized cars tested for fuel consumption gave a mean of 26.4 kilometers per liter with a standard deviation of 2.3.
(a) 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.
(b) Suppose the confidence interval obtained in (a) is too wide. How can the width of this interval be reduced? Describe all possible alternatives. Which alternative is the best and why?
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