Idiot\'s Guides Basic Math and Pre-Algebra

Chapter 20: Measures of Center and Spread 277

Here’s an example with a larger data set and larger numbers. Calculate carefully to find the mean

amount of land in parks and wildlife areas in 2002 in the states shown below.

Land in Rural Parks and Wildlife Areas 2002 (1,000 acres)

Michigan 1,436

Wisconsin 1,000

Minnesota 2,959

Ohio 372

Indiana 264

Illinois 432

Iowa 327

Missouri 649

First add the values given for each of the eight states. The total should be 7,439. Then divide

by 8, because you added up the acreage for eight states. 7,439 z 8 = 929.875. Keep in mind that

the numbers you averaged are in thousands of acres, so the mean you calculated is not actually

929.875 acres, but 929.875 thousand acres or 929,875 acres.

CHECK POINT

Find the mean of each set of data

1. A = {2, 2, 2, 3, 3, 4, 4, 4, 4}


2. B = {34, 54, 78, 92, 101}


3. C = {3, 4, 5, 4, 7, 8, 9, 2, 10, 1}


4. D = {32, 34, 36, 38}


5. E = {2, 2, 3, 4, 5}

Median

The median is the middle value when a set of data has been ordered from smallest to largest or

largest to smallest. You’ve probably heard the word median used in other situations. In geometry,

a median of a triangle connects a vertex to the midpoint of the opposite side. The strip of grass

in the middle of a highway that divides the lanes moving in one direction from the lanes in the

other direction is also called the median. Medians are always about the middle.