Statistics question

Elite_Etnisa

well people, just got a maths question on friday and my teacher didnt really explain how to deal with it never done it before and its a new thing she said just to see if we can understand it.

Example : As part of a lab exp. 19 rats are weighed. Their weight (grams) are given below.

148 158 167 176
188 190 200 149
165 176 186 195
163 176 181 146
164 176 170

a) display the data on a stem plot
find q1 lower
c) find q2 median
d) find q3 upper
e) calculate interquartzile range.

Well thats what it is.

Stem Plot
14 | 6,8,9
15 | 8
16 | 7,5,3,4
17 | 6,6,6,6,0
18 | 8,6,1
19 | 0,5
20 | 0

So thats the stem plot. Everything looks simple enough but in order to answer b c and d i need a graph which i dont know how to draw. Any help ? Thanks

MathsManiac

You don't need a new graph to do (b), (c) and (d).

The median is the number that divides the distribution in half. That is, half the numbers are below it and half are above. So, once the numbers are arranged in order, (as they more or less are on a stemplot,) the median is the middle one.

The quartiles are the same idea except they divide the distribution in quarters. The lower quartile divides the bottom quarter from the top three quarters. The upper quartile divides the top quarter from the bottom three quarters. The middle quartile is the median. If you want, you can think of the lower quartile as the median of the bottom half, and upper one as the median of the top half.

You should be able to read them off the stemplot by counting up or down.

The interquartile range is the difference between the upper and lower quartiles. Like the standard deviation, it is a measure of spread, as it tells you something about how spread out the numbers are.

median = 176; Q1 = 163; Q3 = 186; IQR = 186-163 = 23.