Flashcards in Statistics III Deck (29):

0

## What is the basic idea behind survey sampling?

### simple random sampling

1

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

### ... cluster sampling.

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.

### stratified sampling

4

## What is the correlation coefficient?

### the normalized version of the covariance

5

## What does the correlation coefficient show by its magnitude?

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

6

## What does "normalization" (in its simplest case) mean?

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

7

## What does μ stand for?

### the mean of the population

8

## What does σ stand for?

### the standard deviation

9

## How is the letter σ called?

### Sigma

10

## How is the letter μ called?

### Mu

11

## What's the greek symbol for the "mean"?

### μ

12

## What's the greek symbol for the standard deviation?

### σ

13

## What does it mean to standardize values?

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

14

## What does x-Dach stand for?

### the arithmetic mean

15

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

### z = (x - μ) / σ

16

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

### 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)

17

## About covariance: What does s = 0 mean?

### no association, statistical independence

18

## About covariance: What does s > 0 mean?

### positive association

19

## About covariance: What does s < 0 mean?

### negative associsation

20

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

###
μ(z) = 0

σ(z) = 1

21

## About correlation: What does r = 0 mean?

### no correlation, statistical independence

22

## About correlation: What does r > 0 mean?

### positive correlation

23

## About correlation: What does r < 0 mean?

### negative correlation

24

## What tells us the coefficient of determination?

###
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

25

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

### Yes!

26

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

### No!

27

## What does regression(x, y) tell us?

### The influence of x on y.

28

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

###
x ... predictor variable

y ... response variable

29