Questions Curve Fitting

Consider the following data set:

xy
31.2
41.4
51.6
61.75
71.85

The data is also provided in Q8-1.rda (the data frame is called Q8).

  1. Plot the data, draw the regression line and estimate the equation of the line
  2. What is the correlation coefficient?
  3. Interpolate the y-value for x = 5.5
  4. Extrapolate the y-values for x = 0.1 and x = 15

Consider the extended data set below:

xy
0.1-1.25
0.2-0.7
10.4
20.9
31.2
41.4
51.6
61.75
71.85
81.95
92.05
102.1
122.25
142.35
152.4

The data is also provided in Q8-2.rda (the data frame is called Q8Extended).

    1. Plot these data in a graph
    2. What is the relation between x and y and what is the value of the correlation coefficient?
    3. What are the y-values for x = 0.1 and x = 15?

A Study is undertaken to validate the use of an iPhone inclinometer to measure knee flexion. The ‘Gold Standard’ is a Lafayette Long-Armed Goniometer. Multiple knee flexion angles are measured with each device and the paired data are provided in the file goniometer.rda.

    1. Create a scatterplot with equal axes and add a line x=y.
    2. Calculate the Pearson’s correlation coefficient.
    3. Calculate the Interclass Correlation (ICC).