Statistics III

Question 0

If respondents from small geographically local clusters are chosen, it is called …

Answer 0

… cluster sampling.

Question 1

What is the basic idea behind survey sampling?

Answer 1

simple random sampling

Question 3

How is the procedure, of which the following is an example of, called?
We could randomly choose a number of women from a population, and separately randomly choose a number of men from the population, where the numbers are chosen so that the proportions of males and females are the same as in the population.

Answer 3

stratified sampling

Question 4

What is the correlation coefficient?

Answer 4

the normalized version of the covariance

Question 5

What does the correlation coefficient show by its magnitude?

Answer 5

By its magnitude it shows the strength of the linear relation.

Question 6

What does “normalization” (in its simplest case) mean?

Answer 6

Adjusting values measured on different scales to a notionally common scale (often prior to averaging).

Question 7

What does μ stand for?

Answer 7

the mean of the population

Question 8

What does σ stand for?

Answer 8

the standard deviation

Question 9

How is the letter σ called?

Answer 9

Sigma

Question 10

How is the letter μ called?

Answer 10

Mu

Question 11

What’s the greek symbol for the “mean”?

Answer 11

μ

Question 12

What’s the greek symbol for the standard deviation?

Answer 12

σ

Question 13

What does it mean to standardize values?

Answer 13

To standardize values around their mean and a standard deviation of 1.

Question 14

What does x-Dach stand for?

Answer 14

the arithmetic mean

Question 15

How to calculate the standard score of a raw score x?

Answer 15

z = (x - μ) / σ

Question 16

What does z represent in the calculation of the standard score of a value x?

Answer 16

The absolute value of z represents the distance between the raw score and the population mean in units of the standard deviation. (negative or positive)

Question 17

About covariance: What does s = 0 mean?

Answer 17

no association, statistical independence

Question 18

About covariance: What does s > 0 mean?

Answer 18

positive association

Question 19

About covariance: What does s < 0 mean?

Answer 19

negative associsation

Question 20

What do we know about the mean and the standard deviation of a z-score?

Answer 20

μ(z) = 0
σ(z) = 1

Question 21

About correlation: What does r = 0 mean?

Answer 21

no correlation, statistical independence

Question 22

About correlation: What does r > 0 mean?

Answer 22

positive correlation

Question 23

About correlation: What does r < 0 mean?

Answer 23

negative correlation

Question 24

What tells us the coefficient of determination?

Answer 24

The amount of the variance of y that can be explained with y’s linear dependency with x.
For example:
r = 0.5
r² = 0.25 -> 25 % can be explained

Question 25

Is Cor(x, y) = Cor(y, x) true?

Answer 25

Yes!

Question 26

Is Regression(x,y) = Regression(y,x) true?

Answer 26

No!

Question 27

What does regression(x, y) tell us?

Answer 27

The influence of x on y.

Question 28

In a regression(x, y) how are x and y called?

Answer 28

x … predictor variable

y … response variable

Question 29

What does r² stand for?

Answer 29

The coefficient of determination.