Statistical enquiry cycle

:3

What are the advantages of primary data?

Collection method is known
Accuracy is known
Can find answers to very specific questions

What are the disadvantages of primary data?

Time consuming to collect
Expensive to collect

What are the advantages of secondary data?

Easy to obtain
Cheap to obtain
Data can be more reliable

What are the disadvantages of secondary data?

Method of collection might be unknown
Data might be out of date
May contain mistakes
May be difficult to find answers to specific questions

What are the advantages of a census?

Unbiased
Accurate
Takes whole population into account

What are the disadvantages of a census?

Time consuming
Expensive
Lots of data to handle

What are the advantages of a sample?

Cheaper
Less time consuming
Less data to handle

What are the disadvantages of a sample?

Not completely representative
May be biased

What are sampling units?

People or items that need to be sampled

What is a sampling frame?

A list of all the sampling units

What is the petersen capture recapture method formula?

m/n = M/N

What assumptions does the petersen capture recapture method make?

Population has not changed
Probability of being caught is the same
Marks are recognisable

Simple random sampling method

Uniquely number each member of the population
Randomly select n different numbers using a random number generator

What are the advantages of random sampling?

Sample is more likely to be representative of population
Choice of units is unbiased

What are the disadvantages of random sampling?

Needs a full list of the whole population
Needs a large sample size

What is judgement sampling?

Use your judgement to select a sample

What is opportunity sampling?

Use units that are available at that time

What is cluster sampling?

Use when the data naturally splits into groups
List of clusters is the sampling frame and some clusters are randomly selected to make the sample

What is quota sampling?

Group the population by characteristics and interview a number from each group

What is the method for systematic sampling?

Decide how large the intervals need to be
Pick a random place to start within the first interval
Collect the sample

What is the formula for stratified sampling?

(number in group / total number) x sampling frame

What is a laboratory experiment?

Experiments conducted in a controlled environment

What are the advantages of laboratory experiments?

Easy to replicate
Can control the extraneous variables

What are the disadvantages of laboratory experiments?

Test subjects may behave differently

What are field experiments?

Experiment carried out in test subject’s environment, researcher controls variables

What are the advantages of field experiments?

More likely to reflect real life behaviour

What are the disadvantages of field experiments?

Can’t control extraneous variables
Harder to replicate exactly

What are natural experiments?

Carried out in test subject’s environment, researcher doesn’t control any variables

What are the advantages of observations?

Systematic and mechanical

What are the disadvantages of observations?

Results prone to chance, bias

What are the advantages of personal interviews?

High response rate, many questions can be askedW

What are the disadvantages of personal interviews?

Expensive, interviewer may influence replies

What are the advantages of postal/online survey?

Relatively cheap, large amount of data can be collected

What are the disadvantages of postal/online surveys?

Poor response rate, limited in type of data

How do you minimize inter observer bias?

Each observer should be given guidance on what to focus on and record

What are the advantages of a pilot survey?

Can help identify early problems
Can help in choosing categories for closed questions

What makes a good questionnaire?

Easy to answer
No gaps/overlaps
No vague answers

What is a matched pair test?

Each individual is paired with an individual in the second group who has everything in common apart from the factor being studied

What is reliability?

The extent to which repeated measures yield similar results

What is validity?

The extent to which a test measures what was intended

Why might a matched pair test be used?

To control the effect of variables

What must a pictogram have?

A key
Quantitative data

What are bar charts used for?

Quantitative and discrete data

What is the formula for a comparative pie chart?

r2/r1 = √f2/√f1

What is a cumulative frequency step polygon for?

Discrete data

What does positive skew mean?

Most of the data values are at the lower end
More of the data is less than the mean
The data above the mean has a greater spread than the data below the mean

What is the formula for frequency density?

frequency/class width

Why might diagrams be misleading?

Scales do not start at 0 / are missing
Scales that don’t increase uniformly
Lines drawn too thick
No labels
No key
Colours make some parts stand out

What are the advantages of tables?

Show exact values

What are the disadvantages of tables?

Do not demonstrate patterns or trends clearly

What are the advantages of bar charts and line graphs?

Show trends and patterns

What are the disadvantages of bar or line graphs?

Data can only be read if changes are small

What are the advantages of pie charts?

Show proportions

What are the disadvantages of pie charts?

Do not show accurate data values

What are the advantages of random sampling?

Each sampling unit has an equal chance of being selected

What are the disadvantages of simple random sampling?

Some groups may not be represented

What are the advantages of stratified sampling?

Members selected are chosen randomly
Helps avoid bias

What are the disadvantages of stratified sampling?

Cannot be used if there are no groups/groups overlap

What are the disadvantages of systematic sampling?

Periodic patternsW

What are the advantages of systematic sampling?

Large population

What are the advantages of quota sampling?

Small sample, representative

What are the disadvantages of quota sampling?

Some members might choose not to be included

What are the advantages of oppurtunity sampling?

Sample is needed quickly
Easy
No list

What are the disadvantages of oppurtunity sampling?

Unlikely to be representative, biased

What is the method for stratified sampling?

Population is divided into strata
A random sample is taken from each stratum

What are the advantages of judgement sampling?

Can be made representative of the population
Quick

What are the disadvantages of judgement sampling?

Biased

Why is cleaning data needed?

incomplete responses
non responses
incorrect format
anomalies

What is the advantage of a comparative pie chart?

The area is proportional to frequency

What does positive skew mean?

The data is more spread out above the median than below

What does IQR do?

Measure spread of middle 50% of data

How do you interpret crude rates?

Births/deaths per 1000 people

What are the requirements for a binomial distribution?

Fixed number of trials
Independent
Each trial will only result in success or failure
The probability of success remains constantW

What are the requirements for a normal distribution?

Continuous
Symetrical
Bell shaped

What data is within a normal distribution?

68% - one sd
95% - 2sd
100% - 3sd

Why might a simulation be needed?

It can be used to model real life events
easier and cheaper than collecting and analysing real data

What is the mean for a binomial distribution?

NP