The answer is
7.9306Using the formula in the attached:
Where: xi = sample value; μ = sample mean; n = sample size
1.) Calculate the mean first:
μ = 12.0 + 18.3 + 29.6 + 14.3 + 27.8 / 5
= 102 / 5
μ = 20.4
2.) Using the mean, calculate (xi - μ)² for each value:
(12.0 - 20.4)² = 70.56
(18.3 - 20.4)² = 4.41
(29.6 - 20.4)² = 84.64
(14.3 - 20.4)² = 37.21
(27.8 - 20.4)² = 54.76
3.) Sum the squared differences and divide by n - 1.
μ = 70.56 + 4.41 + 84.64 + 37.21 + 54.76
= 251.58 / 5-1
μ =
62.895 (this is now called sample variance)
4.) Get the square root of the sample variance:
√62.895 =
7.9306
<span>The names of the three eras identified on the x-axis in model 1 answers are Paleozoic, Mesozoic and Cenozoic. It can be seen from the graph that a mass extinction happened 444 million years ago in Paleozoic era, another happened 254 million years ago at end of Paleozoic era and marked the beginning of Mesozoic era. The final mass extinction happened 65 million years ago at end of Mesozoic era in which dinosaurs went extinct.</span>