Question

PROBLEM 6. 10 A histogram has mean 70 and standard deviation 5 If the histogram is not bell shaped but it is symmetric. Find the least proportion of data falls between 70 and 80 If the histogram is bell shaped. Find the proportion of data between 65 and 77

Answer 1

a. 0.4772 = 47.72 %

b. 0.7605 = 76.05 %

Explanation:

What we must do is calculate the z value for each value and thus find what percentage each represents and the subtraction would be the percentage between those two values.

We have that z is equal to:

z = (x - m) / (sd)

x is the value to evaluate, m the mean, sd the standard deviation

a. ind the least proportion of data falls between 70 and 80 If the histogram is bell shaped:

So for 70 copies we have:

z = (70 - 70) / (5)

z = 0

and this value represents 0.5

So for 80 copies we have:

z = (80 - 70) / (5)

z = 2

and this value represents 0.9772

p (70 > x > 80) = 0.9772 - 0.5

p (70 > x > 80) = 0.4772 = 47.72 %

b. Find the proportion of data between 65 and 77

So for 65 copies we have:

z = (65 - 70) / (5)

z = -1

and this value represents 0.1587

So for 77 copies we have:

z = (77 - 70) / (5)

z = 1.4

and this value represents 0.9192

p (65 > x > 77) = 0.9192 - 0.1587

p (65 > x > 77) = 0.7605 = 76.05 %