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

Question

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## Answers ( No )

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