hi the plants are plotted on the y axis and the heights are
plotted on the x axis.
attached is my working graph. i understand what you
mean. look at the 32.5 term of plant on y axis and find
the corresponding median height on the x axis
http://img196.imageshack.us/i/83016747.jpg/
but the answer i obtained is 51.5cm(but answer is wrong)
while if i use graph method: 50%* 64= 32 plants. median= 51cm,
which is the correct answer.
i am confused as if use (n+1)/2 to find median,
median=51.5cm
but if use graph method(which is n/2, 50th percentile), median=
51cm
Generally speaking, since your scale is quite small, where 1
small box = 1cm, the margin for error should be +/- 1.0, and thus
any answer from 50cm to 52cm should be acceptable.
But this is also dependent on how your teacher wish to mark your
paper.
As for the median, the steps for finding it won't change just
because we are drawing it on graph instead of calculating it out on
paper.
For a total of 64 plants, the median will always be 32.5, as
long as the amount of plants do not change.