4.1) The student t-test

The following data table lists gas analyses of the Etna eruption in 1970 and 1971. Determine
whether there are significant differences in gas composition between these eruption. Don't forget
to first test normality (in PAST) and equality of variance.

Hydrogen content (atom%) in gasses from the 1970 and 1971 Etna eruptions.	
1970	1971
	
35.8	42
45.5	57
35.5	42
32.2	54.5
50	35
39	52.5
37	43.5
47	48
38.5	45
36	44.6
40.5	48.5
35.5	63
45.5	55
37	40
36	37.5
53	53.7