Let x- intercept represents time
Let y-intercept represents population
Let 1990 represent initial year
Points are (0,14.2)(10,12.4)
slope m=
=
General linear equation
y= mx+b --------------(i)
here m is slope and b is intercept
plug the 1st point in equation
14.2= -0.018(0) + b
b=14.2
y= 0.018x + 14.2
replace y with p(t) and x with t
p(t) = -0.018t + 14.2
This value is approximate.
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Explanation:
Let's compute the z score for x = 40
z = (x-mu)/sigma
z = (40-47)/7
z = -1
We're exactly one standard deviation below the mean.
Repeat these steps for x = 68
z = (x-mu)/sigma
z = (68-47)/7
z = 3
This score is exactly three standard deviations above the mean.
Now refer to the Empirical Rule chart below. We'll add up the percentages that are between z = -1 and z = 3. This consists of the two pink regions (each 34%), the right blue region (13.5%) and the right green region (2.35%). These percentages are approximate.
34+34+13.5+2.35 = 83.85
<u>Roughly 83.85%</u> of the one-mile roadways have between 40 and 68 potholes.
