Comparing Petrol And Petrol Cars

Question 1:
My answer to case study question is “Yes, they are”. There are proofs showing that petrol (gasoline) cars are more powerful compared to diesel cars. The main difference between diesel cars and petrol cars is the ignition. Petrol engines use spark ignition whereas diesel engines utilize compression ignition. This gives petrol cars a faster, more powerful start and higher BHP(brake horse power), which means higher KW. Chris Rosamond, an author from Auto Express, a weekly motoring magazine in the United Kingdom stated that diesel engine power band was usually relatively narrow when compared to a petrol engine(Chris, 2017). However, Chris was not the first one who said that. Daniel L. Hittler, A.M.C’s director of power-plant engineering

Diesel cars’ minimum power is less than that of petrol cars by 16KW. These figures indicate that diesel cars power band is much lower in comparison with petrol cars.
Since both the standard deviation of diesel and petrol cars are relatively small, the power of diesel and petrol cars fluctuate around their average power(80.56KW and 93.43KW respectively). This is made clearer by the coefficient of variation. There is about 30.53% of cars have the power about the average power of diesel cars, this percentage is 25.5% for petrol cars.

Key Findings:
_Out of 18 diesel cars, 10 cars have power lower than 75KW, and 5 cars have engine power greater than 100KW.
_The first three class of petrol cars possess a relatively equal number of cars(25, 28, and 21 respectively). This also occupies 74 out of 82 petrol cars.

Analysis:
As mentioned above, diesel cars illustrate a clear gap between low power cars and high power cars, only 3 cars are in the middle class. Yet, despite having many cars in the high power class, none of 18 diesel cars have an engine power beyond 115KW.
Most petrol cars have engine powers in the low and middle classes and a minority is in an excessively high power

Analysis:
The box-and whisker plots give us a clearer view of diesel and petrol cars’ power.
While diesel cars’ engine power concentrates around the median at a range of 39.5, the interquartile range of petrol cars’ power is much smaller(25). Diesel power’s statistics tend to be focused within a small area, petrol power’s ones are spread out into a much larger range. The majority of figures fluctuate around 60KW to 120KW, which is a range of about 60, however, the range of petrol power is 108. This is due to the existence of outliers. Petrol cars include some with intensively high power, this contributes to the unexpectedly wide power range.
According to the table, there are 7 petrol cars whose power is higher than 125KW, defined as more powerful. As for diesel cars, none of them have engine power greater than 125KW. This can lead to a conclusion, the type of car( diesel or petrol) and having an engine of at least 125KW are statistically dependent events.
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