To test the claim that the manufacturers have made significant improvement in fuel economy (overall miles per gallon increased in 2019) compared to the average of 25 mpg in 2013, the appropriate null and alternative hypotheses would be:
H0 (Null Hypothesis): μ ≤ 25 (The average mpg in 2019 is less than or equal to 25)
H1 (Alternative Hypothesis): μ > 25 (The average mpg in 2019 is greater than 25)
In this case, we are performing a one-tailed test because we are interested only in the case where the average mpg in 2019 is greater than the 2013 average of 25 mpg. The claim being tested is that the manufacturers have made a significant improvement in fuel economy.
You can use the provided sample data of 65 sedans from different companies in 2019 to calculate a test statistic (e.g., a z-score or t-statistic) and then compare it to a critical value or perform a hypothesis test using the appropriate test (e.g., one-sample t-test or one-sample z-test) to determine if there is enough evidence to reject the null hypothesis and support the claim of a significant improvement in fuel economy.