stats

Question 1

what is a population

Answer 1

whole set of items that are of interest

Question 2

census

Answer 2

observes or measures every member of the population

Question 3

sample

Answer 3

selection of a subset of the population which represents the population

Question 4

sampling units

Answer 4

individual units of a population

Question 5

sampling frame

Answer 5

sampling units that are individually labelled to form a list

Question 6

advantages and disadvantages of census

Answer 6

+ completely accurate
- takes long time
- hard to process large quantity of data
- expensive
- can’t be used when testing process destroys item

Question 7

+ - of sample

Answer 7

+ not time consuming
+ less expensive
+ less data to process
- less accurate
- sample may not be large enough to give info about sub groups of population

Question 8

what is simple random sampling?

Answer 8

where every sampling unit of the sampling frame has equal chance of being selected to avoid bias

Question 9

how to carry out simple random sampling?

Answer 9

• in sampling frame each item has an identifying number
• use random number generator or lottery sample

Question 10

+ - simple random sampling

Answer 10

+ unbiased
+ easy and cheap
+ each number has a known equal chance of being chosen

• not suitable for large sample size
• need sampling frame

Question 11

what is systematic sampling?

Answer 11

required elements are chosen at regular intervals from an ordered list. starting point chosen randomly

Question 12

how to carry out systematic sampling?

Answer 12

take every kth element where
k= population size/ sample size
starting at a number between 1 and k

Question 13

+ - systematic sampling

Answer 13

+ simple and quick to use
+suitable for large sample sizes
- need sampling frame
- can introduce bias if sampling frame not random

Question 14

what is stratified sampling?

Answer 14

population divided into mutually exclusive strata and a random sample selected from each

Question 15

what are strata

Answer 15

distinct group

Question 16

number sampled=

Answer 16

(number in stratum/ number in population) x overall sample size

Question 17

+ - of stratified sampling

Answer 17

+ reflects population structure
+ guarantees proportional representation of groups within populations

• populations need to be classified into distinct strata

Question 18

what is quota sampling

Answer 18

researcher selects sample reflecting characteristics of whole population

Question 19

+ - quota sampling

Answer 19

+ small sample represents population
+no sampling frame
+quick easy inexpensive

• non-random = bias
• dividing into groups may be innacurate
• non responses recorded

Question 20

opportunity sampling

Answer 20

taking sample only from item or people available at the time of study and who fit criteria being looked for

Question 21

+- quota sampling

Answer 21

+ easy
+ inexpensive

-not representative
- dependant on researcher

Question 22

what are 5 uk stations in large data set

Answer 22

Leuchars
Lemming
Heathrow
Hurn
Camborne

Question 23

what are 3 overseas weather stations

Answer 23

• jacksonville
• beijing
  -perth

Question 24

when is data in large data set from

Answer 24

may to october 1987
may to october 2015

Question 25

+ - of mode

Answer 25

+ use when data qualitative or quantitative
- if every value different, mode is useless

Question 26

+- mean

Answer 26

+ uses all data in calculation
- affected by extreme values

Question 27

+- median

Answer 27

+ not affected by extreme values or skewed by outliers
- doesnt take all date into account so less representative

Question 28

4 properties of binomial distribution

Answer 28

• fixed number of trials
• 2 possible outcomes
• trials are independent
• fixed probability of success

Question 29

what is the independent variable

Answer 29

• explanatory
• one that can be changed easily and plotted on x axis

Question 30

what is dependent variable

Answer 30

• response
• one that need to measure
• plotted on y axis

Question 31

properties of normal distribution

Answer 31

• symmetrical about the mean
• mode, median, mean equal
• area under curve=1

Question 32

conditions for normal approximation

Answer 32

• n is large
• p is close to 0.5

Question 33

modelling assumptions for particle

Answer 33

• mass concentrated at single point
• ignore rotational air forces and air resistance so less accurate

Question 34

modelling assumptions for rod

Answer 34

• mass concentrated along line
• no thickness
• rigid so doesn’t bend

Question 35

modelling assumptions for lamina

Answer 35

• mass distributed across flat surface

Question 36

modelling assumptions for uniform body

Answer 36

• mass concentrated at single point at geometrical centre of body

Question 37

modelling assumptions for light object

Answer 37

• treat as 0 mass
• tension equal at both ends of string

Question 38

modelling assumptions for inextensible string

Answer 38

• acceleration same in objects connected

Question 39

modelling assumptions for smooth surface

Answer 39

• no friction

Question 40

modelling assumptions for rough surface

Answer 40

• objects in contact with surface have frictional force when moving or acted upon by force

Question 41

modelling assumptions for wire

Answer 41

• treat as one dimensional

Question 42

modelling assumptions for smooth and light pulley

Answer 42

• no mass
• tension equal

Question 43

modelling assumptions for peg

Answer 43

• dimensionless and fixed
• rough/smooth

Question 44

modelling assumptions for bead

Answer 44

• moves freely along wire
• tension equal on either side

Question 45

modelling assumptions for air resistance

Answer 45

• negligible

Question 46

modelling assumptions for gravity

Answer 46

• assume all masses attracted towards earth
• g constant as 9.8