Wk2 L1 Introduction to statistical variables

Question 1

Define Random?

Answer 1

Random is something where the outcome is uncertain

Question 2

Define what a variable is?

Answer 2

a Variable is a thing that can take many different values

Question 3

Define what a random variable is?

Answer 3

a Random variable is a thing that can take many values, and you can’t predict the outcome in advance

Question 4

Define what a domain is?

Answer 4

A Domain is the set of all possible values (outcomes) of a random variable

Question 5

Define what an event is?

Answer 5

Event: observing one of these possible outcomes in the domain

Question 6

Define what frequency is?

Answer 6

Frequency is the number of times a particular outcome is observed

Question 7

What are the 2 types of Statistical Variable?

Answer 7

The 2 types of Statistical Variable are:

1) Categorical (Qualitative)

2) Numerical (Quantitative)

Question 8

What are the 2 types of Categorical (Qualitative) Variable?

Answer 8

The 2 types of Categorical (Qualitative) Variable are:

1) Nominal (or binary)
2) Ordinal

Question 9

What are the 2 types of Numerical
(Quantitative) Variable?

Answer 9

the 2 types of Numerical
(Quantitative) Variable:

1) Ratio scale
2) Interval scale

Question 10

What is a nominal variable?

Answer 10

A nominal variable is just a name used to represent a category, class or group
{Spain, France, Italy, Germany,…}
{Red, Yellow, Green, Blue, …}
{Jo, Alex, Sara, Dan, …}

It does not indicate size or level

It makes no sense to do numerical calculations with nominal variables (e.g. Spain - France =??)

Question 11

What are binary nominal variables?

Answer 11

binary variables are a class of 2
{True, False}; {Alive, Dead};

Question 12

What are Ordinal categorical variables?

Answer 12

Ordinal categorical variables:

Now there is a logical order to the categories
{Gold, Silver, Bronze}

We still can’t do numerical calculations

Most numerical calculations directly using ordinal data are meaningless

Question 13

What are cardinal variables?

Answer 13

Quantitative Cardinal variables are:

Each level denotes an actual number and there are equal intervals between consecutive levels

Question 14

What are interval variables?

Answer 14

Interval scale variables have no “natural” or true zero: the zero is chosen arbitrarily
E.g. the interval between 12⁰C and 13⁰C is the same as the interval between 55.1⁰C and 56.1⁰C

We can’t use ratios for interval variables: it doesn’t make sense to say 32⁰C is twice as hot as 16⁰C

Question 15

What are ratio variables?

Answer 15

This is the same as an interval variable, except now there is a true, universal zero

Question 16

What is discrete data?

Answer 16

Discrete data is where each data point is distinct and separate, and there are gaps between the points. e.g small medium or large in tshirts

Discrete variables are made up of naturally distinct events: count data which can only take certain values, with gaps between them

Number of goals scored in a football match; number of songs in a playlist; shoe sizes

Not always just whole numbers, but usually

Question 17

What is continuous data?

Answer 17

Continuous data is where there are no gaps anywhere between data. e.g height rather than shoe size

can take any value between some (possibly theoretical) minimum and maximum, with no gaps

Time taken to run a marathon; latitude and longitude on a map; speed of a F1 racing car

Question 18

What are the three sources of primary data?

Answer 18

The three Primary Sources of Data Collection are:

1) Observation

2) survey

3) experimentation

Question 19

What are the two sources of secondary data?

Answer 19

The two sources of secondary data are:

1) print
2) electronic

Question 20

what is the advantage of observation?

Answer 20

The advantage of observation is that it is reliable

Question 21

what is the disadvantage of observation?

Answer 21

The disadvantage of observation is that it is subjective to measuerer

Question 22

what are the two advantages of face to face interview?

Answer 22

the two advantages of face to face interview are:

1) High response rate
2) clarifies questions

Question 23

what are the two disadvantages of face to face interview?

Answer 23

The two disadvantages of face to face interview are:

1) costly
2) open to interpretation by interviewer

Question 24

what are the two disadvantages of a telephone interview?

Answer 24

The two disadvantages of telephone interview are:

1) annoys people
2) bias to those with phones

Question 25

what are the two advantages of a telephone interview?

Answer 25

The two advantages of telephone interview are:

1) high responses
2) cheaper than face to face

Question 26

What is the advantage of a postal interview?

Answer 26

the advantage of a postal interview is that its is relatively cheap

Question 27

What are the two disadvantages of a postal interview?

Answer 27

the two disadvantages of a postal interview are:

1) bias to people who open their mail
2) low response

Question 28

What is the advantage of a panel survey?

Answer 28

the advantage of a postal interview is that its is dynamic over time

Question 29

What are the three disadvantages of a panel survey?

Answer 29

the three disadvantages of a panel survey are:

1) expensive
2) panel may shrink
3) panellists become experts (bias)

Question 30

What is the advantage of a longitudinal survey?

Answer 30

the advantage of a longitudinal survey is long term change

Question 31

What is the disadvantage of a longitudinal survey?

Answer 31

the disadvantage of a longitudinal survey is small sample sizes

Question 32

what are the two advantages of internet/email survey?

Answer 32

the two advantages of internet/email survey are:

1) low response rate
2) bias to those with internet access

Question 33

Define a population?

Answer 33

A population is the whole,
complete set; e.g. all students
at the University of Southampton

Question 34

define a sample?

Answer 34

A sample is a subset (a part) of the population: e.g. all students taking MANG 1019

Question 35

What is bias?

Answer 35

A sample is biased if some parts of the population have a better chance of being represented than others

Question 36

What is a quota sample?

Answer 36

A quota sample specifies that we must include a given number from this subset
E.g. we may be curious to know how many Man Utd supporters actually come from Manchester, so a quota sample would specify that at least 20 (say) students in the sample must be from Manchester

Question 37

What is simple random sampling?

Answer 37

We first need a complete sampling frame, i.e. a list of all members of the population, which we can then use to select our random sample

E.g. as we have an email address for every Southampton student, we could easily pick a random sample to ask

Question 38

What is Stratified random sampling?

Answer 38

Divide population into “strata’’

Each stratum is a group or segment that is distinctive from others

The elements in each stratum are “homogeneous”, i.e. have similar characteristics

E.g. undergrad/postgrad (2 strata); by Faculty (5 strata); by academic discipline (at least 30 strata)

Select a simple random sample from each stratum

Guarantees a “representative” sample