In the case of those girls who do well in both English and arithmetic, there seems to be improved facility in the field of arithmetic.

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English Marks -- ►

Data of W. Garneti in the Journal of the Royal Statistical Society, 1910

Fig. i66. Examination Marks Obtained by 9,396 School Girls in England

Each girl is represented by one dot showing to scale the grade in English and the grade in arithmetic. The dots are arranged uniformly inside of squares formed by co-ordinate lines spaced ten units apart in the scales for marks. The straight diagonal line drawn from zero shows equal ability in the two studies. The heavy wavy line is drawn through points having an equal number of girls represented on either side of the line, and its position proves that girls have much more ability in English than in arithmetic.

GRAPHIC METHODS

The data of Fig. 166 are shown by another method m Fig. 167. Though Fig. 167 appears to represent a soHd model, there was in reahty no sohd model made in order to obtain this illustration. By using isometric paper a chart like Fig. 167 can be made with comparatively little work. Isometric paper has lines ruled on the paper right and left at an angle of 30 degrees to the horizontal. By selecting a vertical scale to portray by separate columns the number of girls represented in any square of Fig. 166, it becomes a comparatively simple matter to draw the illustration.