Some Field Experience in the use of an Accelerated Method in Estimating 28-Day Strength of Concrete" considered regressing y =28-day standard-cured strength (psi) against x =accelerated strength (psi). Suppose the equation of the true regression line is y =1800 +1.3x.

a. What is the expected value of 28-day strength when accelerated strength= 2500? (2 marks)

b. By how much can we expect 28-day strength to change when accelerated strength increases by 1 psi? (4 marks)

c. Answer part (b) for an increase of 100 psi. (2 marks)

d. Answer part (b) for a decrease of 100 ps

Step-by-step explanation:

The given function is

Where represents the accelerated strength in psi, and represents 28-day standard-cured strength in psi.

Part a is about finding the y-value for

Therefore, the expected value of 28-day strength when accelerated strength is 2,500, is 5,050 psi.

Part b is about the y-value for

Part c is about the y-value for

Part d is about the y-value for

solution:

→c= a b , that is product of a and b is possible only when when a is m × n matrix and b is n × p matrix.

that is, number of columns of a= number of rows of b.

so, size of matrix , c= a b is , if a = (m × n)matrix

b= (n × p)matrix

then a b = [ (m × n)matrix] ×[   (n × p)matrix ]

→→c= a b= [m × p ] matrix

→→size of product a b will be equal to = number of rows of a × number of columns of b