Suppose the National Transportation Safety Board (NTSB) wants to examine the safety of compact cars, midsize cars and full-size cars. It collects a sample of five for each of the treatments (car types). Using the hypothetical data provided below, test whether the mean pressure applied to the driver’s head during a crash test is equal for each type of car. Use α = 0.05.

Car Type	Compact (1)	Midsize (2)	Full-Size (3)
	643	469	484
	655	427	456
	702	525	402
	668	501	416
	692	444	438
Sample Mean (X)	672	473.2	439.2
Sample Variance ( si2 )	611.5	1615.2	1053.2