Sampling Techniques

Simple Random SampleKeep Your Index Card Number On You

Table 1 – Random Numbers

92630 78240 19267 95457 53497 23894 37708 79862

79445 78735 71549 44843 26104 67318 00701 34986

59654 71966 27386 50004 05358 94031 29281 18544

31524 49587 76612 39789 13537 48086 59483 60680

06348 76938 90379 51302 55887 71015 09209 79157

The Winners Are!!!!

When you choose members of a sample, you should decide whether it is acceptable to have the some

population member selected more than once. If it is acceptable, then the sampling process is said to be with replacement. If it is not acceptable, then the sampling

process is said to be without replacement.

Replacement

Does Somebody Win More Than Once???

Members of the population are divided into STRATA

Characteristics????

Separate into two subsets – Gender

Hand out Second Set of Index Cards

Stratified Sample

Same number of Ladies and Gentlemen are chosen!!

Members of the population are divided into STRATA

Characteristics????

Separate into three subsets – Low, Medium and High Income

Hand out Third Set of Index Cards

Stratified Sample

Same number people with different incomes are chosen!!

Divide Population into groups called CLUSTERS

Do you all live in Montville Township??

Section of in to different region of Montville Township.

I will choose one of the clusters as my sample.

It is important to make sure that the clusters have similar characteristics!!

Cluster Sample

Back to One Index Card!!

Everyone get in order!!Choose a number between 1 and 6, for our

regular intervals

Systematic Sample

It is the easiest sample but it should be avoided do to regular patterns.

Takes members of a population that are available.

I would like do a surveyTo monitor how students feel when they do too much

math work.

Is any one available to do extra Math Homework???

Convenience Sample

Leads to a Biased Study!!!

1.) Simple Random Sample

2.) Stratified Sample

3.) Cluster Sample

4.) Systematic Sample

5.) Convenience Sample

Review

Chapter 2 – Descriptive Statistics

2.1 – Frequency Distributions and Their Graphs

Sometimes it is possible to collect

all the data for a given population.

Such as the ages of the 50 most powerful women in the world in 2012.

26, 31, 35, 37, 43, 43, 43, 44, 45, 47, 48, 48, 49, 5051, 51, 51, 51, 52, 54, 54, 54, 54, 5, 55, 55, 56, 57, 57,

57, 58, 58, 58, 58, 59, 59, 59, 62, 62, 63, 64, 65, 65, 65, 66, 66, 67, 67, 72, 86

Researchers usually need sample data in order to analyze populations

Frequency Distribution

Organize Data

Histogram

Class Frequency

26 – 34 2

35 – 43 5

44 – 52 12

53 – 61 18

62 – 70 11

71 – 79 1

80 – 88 1

25.5

- 34

.5

34.5

- 43

.5

43.5

- 52

.5

53.5

- 61

.5

61.5

- 70

.5

70.5

- 79

.5

79.5

- 88

.50

4

8

12

16

20

Ages

Add them all and divide by 50

Oldest age – youngest age

Mean and Range

Grouping Data into

Intervals called ClassesAnd forming a

Frequency Distribution

Organize and Describe a Data Set

Class Frequency, f

1 – 5 5

6 – 10 8

11 – 15 6

16 – 20 8

21 – 25 5

26 - 30 4

Frequency Distribution – is table that show classes or intervals of data entries with a count of the number of entries in each class.The frequency f of a class is the number of data entries in the class.

Class Frequency, f

1 – 5 5

6 – 10 8

11 – 15 6

16 – 20 8

21 – 25 5

26 - 30 4

Lower Class Limit – least number that can belong to the class,

Example: 1, 6, 11, 16, 21, 26

Upper Class Limit – greatest number that can belong to the class

Example: 5, 10, 15, 20, 25, 30

The Range is the difference between the maximum and minimum data entries.

Class width are the intervals, the distance from the upper and lower limits of a class.