In: Statistics and Probability
Does knee height predict overall height? Since elderly people may have difficulty standing to have their heights measured, a study looked at predicting overall height (y) in centimeters, from height to the knee (x) in centimeters. Use this data to answer the following questions.
Data looking at knee height (in cm) and overall height (in cm) |
||||||
Knee Height (cm) |
57.70 |
47.40 |
43.50 |
44.80 |
55.20 |
54.60 |
Overall Height (cm) |
192.10 |
153.30 |
146.40 |
162.70 |
169.10 |
177.80 |
Knee height (X) | overall height (Y) | XY | X2 | Y2 | |
57.7 | 192.1 | 11084.17 | 3329.29 | 36902.41 | |
47.4 | 153.3 | 7266.42 | 2246.76 | 23500.89 | |
43.5 | 146.4 | 6368.4 | 1892.25 | 21432.96 | |
44.8 | 162.7 | 7288.96 | 2007.04 | 26471.29 | |
55.2 | 169.1 | 9334.32 | 3047.04 | 28594.81 | |
54.6 | 177.8 | 9707.88 | 2981.16 | 31612.84 | |
Total | 303.2 | 1001.4 | 51050.15 | 15503.54 | 168515.2 |
n = 6
a)
The equation of the least-squares regression line is given by
where
The formula for finding slope is given by
Therefore,the value of the slope = 2.45
b)
The formula for finding intercept is given by
We have
Now
= 42.93
Therefore,the value of the intercept = 42.93
c)
The equation of the least-squares regression line is
When knee height (x) = 65 cm
= 42.93 + 2.45*65
= 202.18
Overall Height = 202.18 cm
Finding mean and standard deviation of X
Mean of X = 50.53
= 6.03
Finding mean and standard deviation of Y
Mean of Y = 166.9
Finding correlation r of x and y
The formula for finding correlation coefficient is given by
= 0.89
The correlation coefficient between x and y is 0.89
It indicates a strong uphill (positive) linear relationship.
Finding coefficient of determination (R2)
coefficient of determination is the square of the correlation coefficient.
coefficient of determination = R2 = 0.892 = 0.7921
R2 of 0.7921 suggests that 79.21% of the dependent variable is predicted by the independent variable.
When knee height (X) = 430 cm
= 42.93 + 2.45*430
= 1096.43
Overall Height = 1096.43 cm
The predicted height for someone with a knee height of 430 cm is 1096.43 cm