Chapter 3
Numerical Descriptions of Data
Section 3.1
Measures of Center
Mean

Add up all data values, then divide by the total number of data values.

Example
1+2+3+4+5
5
=3
ROUNDING RULE: round to one more decimal place than the highest number of
decimal places contained in the data
Weighted Mean

Multiply each data value by its “weight” then divide by the sum of the
weights. Think “per what?” to determine what the weight is.

Example:
Class
Hours
Grade
Weight
Math
3
B
3
English
3
A
4
History
3
C
2
Science
3
A
4
PE
3
F
0
𝑊𝑒𝑖𝑔ℎ𝑡𝑒𝑑 𝑀𝑒𝑎𝑛 = 𝐺𝑃𝐴
3 3 + 3 4 + 3 2 + 3 4 + 3(0)
=
15
9 + 12 + 6 + 12 + 0 39
=
=
= 2.6
15
15
Solution:
a. 3
b. 2.5
Solution:
no mode,
unimodal,
bimodal
Section 3.2
Measures of Dispersion
Calculator Directions

Press STAT

Press edit

In L1 insert data values. If you need to clear data, press up to highlight L1, press clear (not delete), and
press down.

Press 2nd quit (mode)

Press STAT

Arrow over to CALC

Press 1-Var Stats

On the home screen, press 2nd L1 (1)

Press enter

You will then see a list of items.

𝑥 = 𝑚𝑒𝑎𝑛
𝑆𝑥 = 𝑠𝑎𝑚𝑝𝑙𝑒 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛
𝜎𝑥 = 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛

To find the variance, you will square the standard deviation.

If you scroll down you will see the max, min, and median.