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