Session 4 of my data analysis course at BME.

1. session#5 Divényi János @divenyi.janos

2. b.socrative.com
Student login
into room BMEADAT

4. CASE STUDY
election poll

5. Mr. Allen, the candidate for political
Party A will run against Mr. Baker of
Party B for office. Past races between
these parties for this office were
always close, and it seems that this
one will be no exception – Party A
candidates always have gotten
between 40% and 60% of the vote and
have won about half of the elections.
Carl Morris (1987)

6. QUESTION
Mr. Allen needs to know whether he is
going to win the election, so he orders
a poll. Which of the 3 outcomes would
be the most encouraging for him?
(a) Y = 15, n = 20
(b) Y = 115, n = 200
(c) Y = 1046, n = 2000
Carl Morris (1987)

7. How to find answers
to relevant questions
using data

8. QUESTION
DATA
ANALYSIS
PRESENTATION

9. QUESTION
DATA
ANALYSIS

10. P(A|B)
conditional probability
probability that A occurs
given that B has occurred

11. E(Y|X)
cond. expected value
expected value of variable Y
given that X takes a given value

12. ”
A statistician can have his head
in an oven and his feet in ice,
and he will say that on the
average he feels fine.

13. 17,9%
0,0%
10,0%
20,0%
30,0%
40,0%
50,0%
60,0%
70,0%
80,0%
90,0%
100,0%
average bottom 99% top 1%
Income real growth
USA 1993-2012
Source: Saez (2013)

14. 17,9%
0,0%
10,0%
20,0%
30,0%
40,0%
50,0%
60,0%
70,0%
80,0%
90,0%
100,0%
average bottom 99% top 1%
Income real growth
USA 1993-2012
Source: Saez (2013)

15. 17,9%
6,6%
86,1%
0,0%
10,0%
20,0%
30,0%
40,0%
50,0%
60,0%
70,0%
80,0%
90,0%
100,0%
average bottom 99% top 1%
Income real growth
USA 1993-2012
Source: Saez (2013)

16. E(Y|X) = a + bX
linear regression
if E(Y|X) is linear
the regression function is it

17. REGRESSION
GIVES COMPARISON

20. The Case of Berkeley (1973)
University of California, Berkeley
was sued for bias against women
who had applied for admission
to graduate schools there.

21. Men Women
Applicants Admitted Applicants Admitted
ALL 2590 46% 1835 30%
ALL 2590 46% 1835 30%

22. Men Women
Applicants Admitted Applicants Admitted
ALL 2590 46% 1835 30%

23. Department
Men Women
Applicants Admitted Applicants Admitted
A
B
C
D
E
F
ALL 2590 46% 1835 30%

24. Department
Men Women
Applicants Admitted Applicants Admitted
A 825 62% 108 82%
B 560 63% 25 68%
C 325 37% 593 34%
D 417 33% 375 35%
E 191 28% 393 24%
F 272 6% 341 7%
ALL 2590 46% 1835 30%

25. Department
Men Women
Applicants Admitted Applicants Admitted
A 825 62% 108 82%
B 560 63% 25 68%
C 325 37% 593 34%
D 417 33% 375 35%
E 191 28% 393 24%
F 272 6% 341 7%
ALL 2590 46% 1835 30%