Statistick anal za dat
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Statistick á analýza dat. Daniel Svozil Laboratoř informatiky a chemie, FCHT Vojtěch Spiwok, ÚBM, FPBT. Informace. přednášky – základy, opáčko, cvičení – R http ://ich.vscht.cz/~ svozil/teaching.html Další literatura D. J. Rumsey, Statistics for Dummies, 2011

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Statistick á analýza dat

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Statistick anal za dat

Statistická analýza dat

Daniel Svozil

Laboratoř informatiky a chemie, FCHT

Vojtěch Spiwok, ÚBM, FPBT


Informace

Informace

  • přednášky – základy, opáčko, cvičení – R

  • http://ich.vscht.cz/~svozil/teaching.html

  • Další literatura

    • D. J. Rumsey, Statistics for Dummies, 2011

    • D. J. Rumsey, Intermediate Statistics for Dummies, 2007

  • zápočet, zkouška – bude oznámeno


Valuing houses

Valuing houses

How much money should you expect to pay for 1 300 ft2 house?

104 000 $

Same question now with 1 800 ft2 ?

144 000 $


Valuing houses1

Valuing houses

How much money should you expect to pay for 2 100 ft2 house?

168 000 $

21 is just a half between 18 and 24.


What a statistician does

What a statistician does?

  • Look at data

  • Program computers

  • Run statistics software

  • Drink beer


Linear relationship

Linear relationship

Is there a fixed amount per square foot?

No

What if I change 1 400 to 1 300? What is the answer now?

Yes


Scatter plots bodov graf

Scatter plots (bodový graf)

  • Please, take a pen and a paper and draw a scatter plot of these data.

PRICE

SIZE


Scatter plots

Scatter plots

Is there a fixed price per square foot?

No


Scatter plots1

Scatter plots

What do you think, is the data linear?

Let’s make a scatter plot.

Surprisingly, the data is linear, even if there is no fixed price per square foot!

PRICE = AA x SIZE + BB

PRICE = 30 x SIZE + 2 000


Scatter plots2

Scatter plots

Draw scatterplot and tell me if these data are linear (i.e., do they lie in a line?).

outliers


Bar chart

Bar chart

Warm up. Are these data linear?

No

How much to pay for a 2 200 ft2 house? Just simply interpolate.

105 000

Do you have trust in this number?


Bar chart1

Bar chart

  • Take your data and pull them together.


Bar chart2

Bar chart


Bar chart3

Bar chart

  • Much finer representation of the data

  • Bar chart allows you to understand global trends

  • Statistician uses cumulative tools (such as bar graph) to gain the understanding of the underlying data.


Histograms

Histograms

  • Special case of bar chart.

  • Bar chart looks at 2D data, histogram to 1D data. That is the main difference.


Age distribution

Age distribution

  • Draw a histogram at the paper with the bins by 10 years (i.e. 0-10, 11-20, …)

29

27

14

21

12

9

17

14

32

39

3

9

4

33

38

29

21

31

8

15


V kov pyramida

Věková pyramida

věková pyramida (strom života)

grafické znázornění věkové struktury obyvatelstva

source: http://cs.wikipedia.org/wiki/V%C4%9Bkov%C3%A1_pyramida


Histogram

Histogram

  • Now I will collect heights of all of you in this room.

  • Use Interactive Histogram Applet: http://www.shodor.org/interactivate/activities/Histogram/

  • interval, bin


Histogram body fat

Histogram – Body fat

  • In Interactive Histogram Applet – choose „Body fat % in 252 men“ dataset.

  • Find reasonable bin size

  • Answer following questions. No matter of bin size what is always true?

  • Most scores fall around 20%.

  • The shape is roughly symmetrical.

  • Most scores fall in the middle of distribution.

  • There are more scores between 15 and 25 than between 35 and 50.

  • There are more scores between 0 and 10 than between 18 and 24.

  • Relatively more men have a body fat above 35% or below 5%.


Histogram income distribution

Histogram – Income distribution

  • United States Census Bureau – http://www.census.gov


Histogram income distribution1

Histogram – Income distribution

  • This is an example of a (positively) skewed distribution (zprava zešikmené rozdělení).

  • This distribution is not symmetrical.

  • Most incomes fall to the left of the distribution.


Pie charts

Pie charts

  • koláčový graf

  • elections

    • Party A – 50%

    • Party B – 50%

    • Party A – 724 000 votes

    • Party B – 181 000 votes


Statistick anal za dat

A

B

C

D

E


Pie charts1

Pie charts

  • Party A – 175 000

  • Party B – 50 000

  • Party C – 25 000

  • Party D – 50 000

  • Please, draw the pie chart

A: 4/12

B: 2/12

C: 1/12

D: 2/12


Bar chart and scatter plot

Bar chart and scatter plot

  • Which scatter plot corresponds to this bar chart?


Pie chart to histogram

Pie chart to histogram

  • Which histogram looks like it cames from the same data?


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