Answer:

We can find the second moment given by:

And we can calculate the variance with this formula:
![Var(X) =E(X^2) -[E(X)]^2 = 7.496 -(2.5)^2 = 1.246](https://tex.z-dn.net/?f=%20Var%28X%29%20%3DE%28X%5E2%29%20-%5BE%28X%29%5D%5E2%20%3D%207.496%20-%282.5%29%5E2%20%3D%201.246)
And the deviation is:

Step-by-step explanation:
For this case we have the following probability distribution given:
X          0            1        2         3        4         5 
P(X)   0.031   0.156  0.313  0.313  0.156  0.031
The expected value of a random variable X is the n-th moment about zero of a probability density function f(x) if X is continuous, or the weighted average for a discrete probability distribution, if X is discrete.
The variance of a random variable X represent the spread of the possible values of the variable. The variance of X is written as Var(X).  
We can verify that:

And 
So then we have a probability distribution
We can calculate the expected value with the following formula:

We can find the second moment given by:

And we can calculate the variance with this formula:
![Var(X) =E(X^2) -[E(X)]^2 = 7.496 -(2.5)^2 = 1.246](https://tex.z-dn.net/?f=%20Var%28X%29%20%3DE%28X%5E2%29%20-%5BE%28X%29%5D%5E2%20%3D%207.496%20-%282.5%29%5E2%20%3D%201.246)
And the deviation is:

 
        
             
        
        
        
Answer:
The linear function that discribes the size of the population in function of the t in years is p = 700t - 1,397,300
Step-by-step explanation:
A linear function is defined by a line, so in order to determine the linear function we can use the two points that were given to us to create a line equation and use that as our linear function. The points given to us were (2009; 9000) and (2014; 12500), in this case the year is our value of "x" and the size of the population is our value of "y". The first step is to find the slope of the line which is given by:
m = (y2 - y1)/(x2 - x1)
m = (12500 -9000)/(2014 - 2009) = 3500/5 = 700
Then we can use the slope and the first point to build the equation:
p - 9000 = 700*(t - 2009)
p = 700t - 1406300 + 9000
p = 700t - 1397300
 
        
             
        
        
        
30 times as many students than teachers
Equation = 450/30 = 15 teachers
        
                    
             
        
        
        
Im pretty sure x y should be 30, I hope this helps.