## How strongly do physical characteristics of sisters and brothers correlate? here are data on the heights (in inches) of 11 adult pairs:8?

Question

How strongly do physical characteristics of sisters and brothers correlate? here are data on the heights (in inches) of 11 adult pairs:8?

0

1. Answer: moderate (r = 0.516).

These are data on the heights (in inches) of 11 adult pairs, that you forgot to include with your question:

Brother
71
67
66
70
70
71
70
73
72
65
66

Sister
69
64  65
63
65  62
65
64
66
59
62

The strenght of the correlation of two variables can be determined by the correlation coefficient, r.

A perfect positive correlation has r value equal to 1.

A perfect negative correlation has r value equal to – 1.

A correlation coefficient r between 0.7 and 1 shows a strong correlation.

A coefficiaent around 0.5 is moderate, and a coefficient whose absolute value is below 0.3 is weak.

You have to use a graphing calculator, a worksheet program, or a special program to calculate this statistics.

I used Excel and obtained r = 0.516. So, that shows a moderate correlation.

To use Excel’ tools to calculate r, follow these steps:

1) Enter the data for brothers is a colum and the data for sisters in the colum next to brother’s.

In this way:

Brother
Sister

71
69

67
64

66
65

70
63

70
65

71
62

70
65

73
64

72
66

65
59

66
62

2) Select all the data (you may or may not include the name of the variables)

3) Go to the main bar and choose insert

4) Go to the main bar and choose graph, dispersion

That will show the points in a scatterplot.

5) Change to the version of the graph that contains the line joining the dots and the formulas for y and r^2

6) calculate r as the square root of r^2.

I got r^2 = 0.2667, from which r = 0.5164