Flashcards in Statistics - AS Deck (31)

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1

## What is a population?

### is the whole set of items that are of interest.

2

## What does a census do?

### Observes or measures every number of a population.

3

## What is a sample?

### Is a selection of observations taken from a subset to find out information about the population as a whole.

4

## What is a simple random sample?

### of size n is one where every sample of size n has an equal chance of being selected.

5

## What is systematic sampling?

### the required elements are chosen at regular intervals from an ordered list.

6

## What is stratified sampling?

### the population is divided into mutually exclusive strata & a random sample is taken from each.

7

## What is the equation for sampled in a stratum?

### (no. in stratum/no. in population) * overall sample size

8

## What is quota sampling?

### an interviewer or researcher selects a sample that reflects the characteristics of the whole population.

9

## What is opportunity sampling?

### consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for.

10

## What is quantitative data/variables?

### Data/variables associated with numerical observations.

11

## What is qualitative data/variables?

### Data/variables associated with non-numerical observations.

12

## What is a continuous variable?

### a variable that can take any value in a given range.

13

## What is a discrete variable?

### a variable that can take only specific values in a given range.

14

## What are classes?

### data presented in a grouped frequency table, the specific data values are not shown.

15

## What are the class boundaries?

### The max & min values in each class.

16

## What is the midpoint of a class?

### the middle value of the class boundaries.

17

## What is the class width?

### the difference between the upper & lower class boundaries.

18

## What is the daily mean temperature - large data set?

### this is the average of the hourly temp readings during a 24hr period.

19

## What is the daily total precipitation - large data set?

### The total amount of precipitation recorded in a 24hr period.

20

## What is the daily total sunshine - large data set?

### recorded to the nearest tenth of an hour.

21

## What is the daily mean wind direction & speed - large data set?

###
Mean wind direction are given as bearings & as compass directions.

The data for wind speed is categorised according to the Beaufort scale.

22

## What is Beauforts scale?

### is an empirical measure that relates wind speed to observed conditions at sea or on land.

23

## What is the daily maximum gust?

### this is the highest instantaneous windspeed recorded. The direction from which the maximum gust was blowing is already recorded.

24

## What is the daily maximum relative humidity?

### given as a percentage of air saturation with water vapour. Relative humidities above 95% give rise to misty & foggy conditions.

25

## What is the daily mean cloud cover?

### measured in ‘oktas’ or eighths of the sky covered by cloud.

26

## What is the mean visibility measured in decametres (Dm)?

### This is the greatest horizontal distance at which an object can be seen in daylight.

27

## What is the mean pressure?

### measured in hectopascals (hPa)

28

## What is the null hypothesis h0?

### Is the hypothesis that you assume to be correct.

29

## What is the alternative hypothesis H1?

### Tells you about the parameter if your assumption is shown to be wrong.

30