Section 1.2 Part 2
13
Section 1.2 Part 2 AP Statistics September 11, 2008 Berkley High School, D1B1
-
Upload
cassandra-lott -
Category
Documents
-
view
28 -
download
2
description
Section 1.2 Part 2. AP Statistics September 11, 2008 Berkley High School, D1B1. Describing with Numbers: Spread/Standard Deviation. s 2 is called the variance, and its in units 2 s is called the standard deviation, and its in units. Describing with Numbers: Spread/Standard Deviation. - PowerPoint PPT Presentation
Transcript of Section 1.2 Part 2
Section 1.2Part 2
AP StatisticsSeptember 11, 2008Berkley High School, D1B1
AP Statistics, Section 1.2, Part 2 2
Describing with Numbers: Spread/Standard Deviation s2 is called the
variance, and its in units2
s is called the standard deviation, and its in units.
2)(1
1xx
ns i
1
)()()( 222
212
n
xxxxxxs n
AP Statistics, Section 1.2, Part 2 3
Describing with Numbers: Spread/Standard Deviation s measures spread about the mean and
should be used only when the mean is chosen as the measure of center
s equals 0 only when there is no spread. This happens only when all observations have the same value.
s is not resistant. Outliers effect it adversely.
AP Statistics, Section 1.2, Part 2 4
Calculating s by hand
Observation(x-bar)
Deviation(x-sub-i – x-bar)
Squared Deviation
1792
1666
1362
1614
1460
1867
1439
Sum = 11200
Mean = 1600
AP Statistics, Section 1.2, Part 2 5
Calculating s by hand
Observation(x-bar)
Deviation(x-sub-i – x-bar)
Squared Deviation
1792 1792-1600 = 192
1666 1666-1600 =66
1362 1362-1600 =-238
1614 1614-1600 =14
1460 1460-1600 =-140
1867 1867-1600 =267
1439 1439-1600 =-161
Sum = 11200
Mean = 1600
Sum = 0
AP Statistics, Section 1.2, Part 2 6
Calculating s by hand
Observation(x-bar)
Deviation(x-sub-i – x-bar)
Squared Deviation
1792 1792-1600 = 192 192 * 192 = 36864
1666 1666-1600 =66 4356
1362 1362-1600 =-238 56644
1614 1614-1600 =14 196
1460 1460-1600 =-140 36864
1867 1867-1600 =267 71289
1439 1439-1600 =-161 25921
Sum = 11200
Mean = 1600
Sum = 0 Sum = 214870
AP Statistics, Section 1.2, Part 2 7
Calculating s by hand
67.35811
6
21487017
214870
2
2
2
s
s
s
24.189
67.35811
s
s
AP Statistics, Section 1.2, Part 2 8
Calculating s using TI-83
AP Statistics, Section 1.2, Part 2 9
Calculating s using TI-83
AP Statistics, Section 1.2, Part 2 10
Calculating s using TI-83
AP Statistics, Section 1.2, Part 2 11
Linear Transformations
Adding “a” does not change the shape or spread
Adding “a” does change the center by “a”
bxay
AP Statistics, Section 1.2, Part 2 12
Linear Transformations
Multiplying by “b” does change the shape or spread by “b”
Multiplying by “b” does change the center by “b”
bxay
AP Statistics, Section 1.2, Part 2 13
Assignment
Exercises 1.40 – 1.47, The Practice of Statistics.
