Linear Interpolation

Question 1

How do you find the value of an unknown data point that lies between 2 known data points on a graph

Answer 1

1.Assume there is a straight line goign through the 2 known points
2.Find the equation of the line
3.Use the equation of the line to find the missing point

Question 2

How do we find an unknown data point that lies between 2 known data points in a table

Answer 2

1.Use the equation for linear interpolation
x-x1 y-y1
—— = ——-
x2-x1 y2-y1
Where x1,y1 and x2,y2 are the values of the known data points and x,y are the values of the unknown data points

2.Make y the subject as if it were the equation of a straight line

3.Substitute values into the equation to get an answer

Question 3

How do we find the unknown value of a data point that between a class in a grouped frequency table (x-y y-z)