Link to download Jamovi: https://www.jamovi.org/download.html

The data file https://osf.io/t7brz/quickfiles contains information from the United States of America for 18 randomly sampled motor vehicles. The data was collected to investigate whether there are differences in fuel economy for motor vehicles with differing drive types.

The two variables of interest here are MPG City and DriveTrain. The MPG variable is a measure of distance travelled per gallon of fuel used when driving in a city environment. The larger this number the more fuel efficient the vehicle is. The drive train variable indicates what wheels of the vehicle are mechanically driven from the engine.

It is expected that front wheel drives have the best fuel economy, followed by rear wheel drives and then all wheel drives. This is due to the mechanical losses in the drive train.

For the following, use a significance level of 5%.

(a) Plot the data and provide a preliminary assessment of whether there appears to be differences between fuel efficiency based on drive type.

(b) Carry out an appropriate hypothesis test to for differences in fuel efficiency for the different drive types. Make sure to report the hypotheses tested, test statistic, null distribution, p-value and conclusion in plain language.

(c) If appropriate, carry out post-hoc tests and report the results of each comparison making sure you justify your conclusions. If post-hoc testing is not appropriate, explain the purpose of post-hoc tests and why they are not appropriate in this example.

(d) Assess the assumptions of the test you performed in part (b).