Flashcards in stats Deck (20):

1

## sample

### set of data values for a random variable

2

## population

### a group that you want to sample information about.

3

## sampling frame

### a collection of the items available to be sampled

4

## sample survey

### when information is collected from a small representation of the population

5

## sampling unit

### the person/object to be sampled

6

## sampling fraction

### the proportion of available sampling units that are actually sampled

7

## census

### when all the population has information collected about them

8

## simple random sampling

### every item in a population has an equal chance of being chosen. each item is assigned an ID and a random number table/generator is used to chose a random sample of numbers. suited to a small population.

9

## opportunity/convenience sampling

### sampling due an easy opportunity. leads to bias and an unrepresentative sample however useful for initial studies

10

## stratified sampling

###
the population is divided into categories then a random sample is chosen from each category.

each categories size is proportional with the population.

11

## cluster sampling

###
the population is divided into strata representative of the population. a random sample of clusters is chosen and every item in the chosen clusters is sampled.

a large number of small clusters is most accurate.

12

## systematic sampling

###
a simple rule/pattern is used to chose the sample. Every item in the sampling frame is listed and every nth term is selected.

simple and quick but may be unrepresentative if a pattern exists in the list

13

## quota sampling

###
the population is divided into groups and a given number from each group is sampled.

cheap and quick

14

## self-selecting sample

###
where people volunteer to taake part or are given a choice to participate.

may be bias as people may chose to express their opinions of certain matters.

15

## unimodal

### one bump

16

## bimodal

### two bumps

17

## positively skewed

### bump near beginning

18

## negatively skewed

### bump near end

19

## median

### n+1/2

20