The increasing levels of global warming has led to climate pattern changes. The average number of yearly storms in a ran

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The increasing levels of global warming has led to climate
pattern changes. 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. Then
a.) We conduct a paried samples t test assuming equal but
unknown population variances.
b.) We conduct an independent samples t test assuming unequal
but known population variances.
c.) We conduct an independent samples t test assuming equal but
unknown population variances.
d.)We conduct a paired samples t test assuming unequal but known
population variances.