Statistics is the study of the collection, organization, analysis, interpretation, and presentation of data . It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments.

A statistician is someone who is particularly well versed in the ways of thinking necessary for the successful application of statistical analysis. Such people have often gained this experience through working in any of a wide number of fields. There is also a discipline called mathematical statistics that studies statistics mathematically.

The word statistics, when referring to the scientific discipline, is singular, as in "Statistics is an art. This should not be confused with the word statistic, referring to a quantity (such as mean ormedian) calculated from a set of data, whose plural is statistics ("this statistic seems wrong" or "these statistics are misleading").

Descriptive Statistics:

Methods of organizing, summarizing and presenting data in an informative way.

Inferential Statistics:

Methods used to estimate a property of a population on the basis of a sample.

Population:

The entire set of individual or objects of interest or the measurements obtained from all individuals or objects of interest.

Sample:

A portion, or part, of the population of interest.

TWOTWO T TYPESYPES of of STATISCA DATASTATISCA DATA

Quantitative data are obtained from the result of numerical recording (in the form of figures).

Qualitative data are data related to the category or characteristic of an object .

MEASURES OF CENTRAL TENDENCY

THE MEASURES OF CENTRAL TENDENCY CONSIST OF THREE MEASURES, NAMELY :

Mean (arithmetic mean)

Mode (the value that occurs most often)

Median (the middle value)

Symbol check

∑

xi

i=1

n∑

Sigma: Means the ‘sum of’

Sigma (1 to n) x of i: means add all values of i from 1 to n in a data set

Xi = the ith data point

7

8

Σi = 1

n

xi

n

Refer to handout on notationRefer to handout on notation

See example on next slideSee example on next slide

Mean

Sum of all observations divided by the number of observations

In notation:

Mean uses every item of data but is sensitive to extreme ‘outliers’

MODE

• The Mode means the value that occurs most frequently

Mode= the value that appears most frequency

MEDIAN

• The median is a measure of central tendency used to analyze data.when the collected data are ordered,the data value which lies in the middle (the middle value of data)is called the median

Graphic Presentation of Qualitative Data

Bar Chart: •The classes are reported on the horizontal axis•The class frequencies on the vertical axis•The class frequencies are proportional to the heights of the bars.

Example: Ice cream 20 vendors Ice Cream Sales

Vanilla, 68Choco, 69

50

55

60

65

70

Choco Vanilla

Types

Axi

s Choco

Vanilla

Pie Chart: •Shows the proportion or percent that each class represents of the total number of frequencies

Example: Ice cream 20 vendors

Graphic Presentation of Qualitative Data

Example:

Graphic Presentation

HistogramHistogram

Example:

3. Graphic Presentation

PolygonPolygon

Not floating in the air

OUR SURVEY

In class 8B, there are 23 students.After survey in class 8B, we get the data about:

• Most subjects preferred

• Most subject not preferred

• Opinion about math

VALUES FREQUENCY

SCIENCE 1IPS 13

JAPANESE 2MATH 4

ENGLISH 1ART 1

TOTAL 22

MEAN1x3+1x2+1x4+1x13

622 6 =3.66

MEDIAN22 2 =11 (IPS)

FAVORITE SUBJECTS-Pie Charts

SCINECE4%

IPS57%

JAPANESE9%

MATH18%

FRANCE4%

ENGLISH4% ART

4%

FAVORITE SUBJECTS-Bar Diagram

0

2

4

6

8

10

12

14

Amount

FAVORITE SUBJECTS

0 2 4 6 8 10 12 14

IPA

IPS

JAPANESE

MTK

FRANCE

ENGLISH

ART

Amount

DISLIKE SUBJECTS

VALUES FREQUENCY

PD 1

SCIENCE 11

OR 1

IPS 3

CIVIC 2

MEANMEAN1x11+1x3+1x2x2+1 622 6 =3.66

MEDIAN22 2 =11 (SCIENCE)

MODE(SCIENCE)

DISLIKE SUBJECTS-Pie diagram

DISLIKE SUBJECTS

DISLIKE SUBJECTS

EXERCISE

Jumlah lulusan SMP kelas IX dari suatu daerah dapa tahun 2001 sampai 2004 adaalah sebagai berikut:

TAHUN JUMLAH

2001 20

2002 40

2003 50

2004 70

Nyatakan data di atas dalam bentuk diagram batang

PENDIDIKAN JUMLAH

SD 100 orang

SMP 500 orang

SMA/SMK 2.100 orang

PERGURUAN TINGGI 900 orang

JUMLAH PENDUDUK 3.600

Jumlah dari suatu kelurahan sebanyak 3.600 orang,dengan berbagai tingkat pendidikan sebagai berikut:

Jika Data tersebut di buat diagram lingkaranmanak tentukan,a.Besarnya sudut sektor lingkaran untuk pendidikan SD,SMP,SMA/SMK dan

Perguruan Tinggib.Diagram lingkaran

Diagram Lingkaran di samping menunjukan kendaraan yang di gunakan siswa untuk berangkat ke sekolah,jika jumlah seluruh siswa adalah 500,Banyak siswa yang berankat sekolah menggunakan sepeda adalah ...

A.123B.100C.321D.120

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