Question

The torque. T Nm, required to rotate shafts of different diameters, D mm, on a machine has been tested and recorded below.

D (mm)	6	9	17	21	35	42
T (Nm)	4.4	5.9	10.4	12.6	20.3	24.6

a) Use the method of least squares to determine the linear regression equation that relates the torque to the diameter. Use 3 decimal places for the figures.

b) Using your answer for part a), estimate the value of torque required when the diameter is 11mm to 2 decimal places

c) Calculate the co-efficient of correlation between these variables to 4 decimal places.

d)

Which of the following does your answer in part c indicate - explain how/why?

• A perfect positive linear relationship

• A strong positive linear relationship

• No linear relationship

• A weak negative linear relationship

Answer 1