The increasing levels of global warming has led to climate pattern changes all over the world. The average number of yea

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The increasing levels of global warming has led to climate
pattern changes all over the world. The average number of yearly
storms in a random sample of tropical countries during the 30 year
period 1961-1990 was 94 with a standard deviation of 25, while the
average number of yearly storms in a random sample of tropical
countries during 1991-2020 was 123 with a standard deviation of 32.
A climatologist is interested to gather evidence regarding whether
the average number of storms have increased in 1991-2020 as
compared to 1961-1990. To this purpose she decided to do a t-test.
The degrees of freedom of the t-test is
a.)58
b.) None of the others
c.) 28
d.) 59
e.) 29