The combined city/highway fuel economy of a 2016 Toyota 4Runner 2WD 6-cylinder 4-L automatic 5-speed using regular gas is a normally distributed random variable with a range 13 mpg to 17 mpg. (a) Estimate the standard deviation using Method 3 (the Empirical Rule for a normal distribution) from Table 8.11. (Round your answer to 4 decimal places.) Standard deviation (b) What sample size is needed to estimate the mean with 98 percent confidence and an error of +0.25 mpg? (Enter your answer as a whole number (no decimals). Use a z-value taken to 3 decimal places in your calculations.) Sample size
