chapter 1 Flashcards
what is quantitative data?
numerical observations or measurements
what is qualitative data?
non-numerical observations
quantitative data is either?
continuous or discrete
what is continuous data?
can take any value on a continuous numerical scale such as length or mass
what is discrete data?
can only take particular values on a continuous numerical scale such as shoe size or number of pets
categorical data can be sorted into what type of categories?
non-overlapping
how can ordinal data be written?
in order or can be given a numerical rating scale
what does bivariate data involve?
pairs of related data
what does multivariate data involve?
sets of 3 or more related data values
how can discrete data be grouped?
into classes that do not overlap
do class intervals need to be equal widths?
- no
- use narrower intervals where the data is close together and wider intervals where the data is spread out
what is primary data?
data that has been collected yourself
why are calculations based on grouped data less accurate than those based on raw data?
in grouped data, individual data values are not known so you can only calculate estimates of the mean, median and mode
what do class intervals have to be for continuous data?
class intervals must not have gaps in between them or overlap eachother
what is secondary data?
data that has been collected by someone else
advantages of primary data?
- collection method is known
- accuracy is known
- can find answers to specific questions
what are the disadvantages of primary data?
- time- consuming to collect
- expensive to collect
what are the advantages of secondary data?
- easy and cheap to obtain
- data from some organisations (e.g. Office for National Statistics in the UK) can be more reliable than data you collect for yourself
disadvantages of secondary data?
- method of collection unknown
- data may be out of date
- may contain mistakes
- may come from an unreliable source
- may be difficult to find answers to specific questions
when you are investigating a hypothesis what is the group you are interested in?
the population
what is the population?
everything or everybody that could possibly be involved in the investigation
what is a census?
a survey or investigation with data taken from every member of a population
in the UK how often is a National Census conducted?
every 10 years
what does the National Census collect data about?
collects information about the people living in each home
what do governments use the National Census for?
they use this data to help plan housing, schooling and healthcare provision
in a survey what can you take from the population?
a sample
what does a sample contain?
information about part of the population
to avoid bias what should the sample represent?
the characteristics of the population
what can the results from the sample be used to make?
conclusions for the whole population
advantages of a census?
- unbiased
- accurate
- takes the whole population into account
disadvantages of a census?
- time- consuming
- expensive
- difficult to ensure the whole population is used
- lots of data to handle
advantages of a sample?
- cheaper
- less- time consuming
- less data to handle
disadvantages of a sample?
- not completely representative
- may be biased
the larger the sample….
the more reliable the results
a sample that is too small or selected unfairly can do what to the results…
bias the results
what are the sampling units?
the people or items that are to be sampled
what is a sampling frame?
a list of all of the sampling units
when is the Peterson Capture-Recapture method used?
- a method for estimating the size of the population
- use it to estimate animal/ insect populations where it would be impossible to catch them all and count all of them
the capture re-capture method makes what assumptions: population?
- the population has not changed- no members have entered or left the population
- no births/ deaths between the release and the recapture time
the capture re-capture method makes what assumptions: probability?
the probability of being caught is equal for all individuals
the capture re-capture method makes what assumptions: marks/ tags?
marks/ tags are not lost and are always recognisable
capture re-capture method makes what assumptions: sample size?
the sample size is large enough to be representative of the whole population
in a random sample every member of the population has what kind of chance of being included?
an equal chance
why is a random sample good?
it is fair/ unbiased and better represents the population
how to take a random sample?
- can number each item in the sampling frame
- select the numbers for your sample by using a random number table/ random number generator
advantages of random sampling?
- more likely to be representative of the whole population- provided it is large
- choice of members of sample is unbiased
disadvantages of random sampling?
- needs a full list of the whole population
- needs a large sample size
what is judgement sampling?
using your judgement to select a sample that is representative of the whole population
what is opportunity sampling?
use the people or objects that are available at the time
what is cluster sampling?
- when the data splits naturally into groups e.g. geographical areas
- the list of clusters is the sampling frame
- some clusters are randomly selected from it to make the sample
what is systematic sampling?
- choose a starting point from the sampling frame at random
- choose items at random intervals e.g. every 5th person on a list
what is quota sampling?
group the population by characteristics such as age/ gender and interview a number (quota) from each group e.g. 10 males over 25
how to decide whether a sampling method is suitable?
- whether the sample will be biased
- whether the sample size is sensible
- how quick and easy the method is
- how expensive it is to carry out
what is a stratified sample?
- contains members of each stratum in proportion to the size of that stratum
- the sample from each stratum is selected randomly
what is a data collection sheet?
a table/ tally chart for recording your results
what is the explanatory variable?
the independent variable- the variable you change
what is the response variable?
the variable you are measuring
what are extraneous variables?
variables you are not interested in but they could affect your experiment
what is a laboratory experiment?
experiments conducted in a controlled environment
advantages of laboratory experiments?
- easy to repeat- you can copy the experiment exactly
- you can control all extraneous variables
disadvantages of laboratory experiments?
test subjects may behave differently in test subjects than in real life
what is a field experiment?
- experiments carried out in test subjects everyday environment
- researcher sets up the situation and controls one or more variables
what is an advantage of field experiments?
more likely to reflect real life behaviour
what is a disadvantage of field experiments?
- can’t control extraneous variables
- harder to repeat/replicate the experiment exactly
what is a natural experiment?
experiments carried out in test subjects everyday environments- researcher has no control over variables
what is an advantage of a natural experiment?
more likely to reflect real life behaviour
what is a disadvantage of a natural experiment?
- can’t control the variables
- harder to replicate the study exactly
if replicating or repeating the data gives very similar data what does this show about the data?
it is very valid and reliable
what is a questionnaire?
a set of questions designed to obtain data
what is the person completing the questionnaire called?
a respondent
what type of answers do open questions have?
no suggested answers
what type of answers do closed questions have?
gives answers to choose from
why can open questions be difficult?
each respondent could give a different answer- could be difficult to summarise and analyse the answers
what could you use for closed questions?
an opinion scale
what is the problem with opinion scales?
- most people will answer somewhere along the middle
- they are unlikely to express a strong opinion either way as they do not want to seem extreme
how can questions in questionnaires be biased?
- the boxes do not cover all different possibilities
- boxes cover one opinion more than once
- biased questions that try and persuade you to agree with the statement
in questionnaires what should questions be like?
- keep questions short and use simple language
- avoid biased or leading questions that suggest a particular answer
- give intervals that do not overlap
- include a time frame
advantages of interviews?
- interviewer can explain questions
- interviewer can put people at ease when asking personal questions
- respondent can explain answers
- high response rate- every person interviewed answered the questions
disadvantages of interviews?
- respondents may be less honest in a face-to-face setting and less likely to answer personal questions truthfully
- interviewing can take a long time- can also be expensive
- sample size is smaller than with a questionnaire
- interviewer bias- interviewer may interpret answers to suit their own opinions
- respondents may try to impress the interviewer or say the answers they think the interviewer wants to hear
anonymous questionnaire advantages?
- respondents are more likely to be honest and more likely to answer personal questions
- respondents can all complete the questionnaire at the same time or in their own time so it can be quick and cheap
- easy to send questionnaires to a large and representative sample
- no interviewer bias
disadvantages of anonymous questionnaires?
- respondent may not understand the questions
- researcher may not understand the respondent’s answers
- lower response rate- some people may not answer all of the questions or return the questionnaires
why would people conduct a pilot survey before their actual survey?
- to check that respondents understand the questions
- closed questions include all the likely answer questions
- the questionnaire collects the information needed
what does a random response method use?
a random event
what is an outlier or anomalous data value?
a value that does not fit the pattern of the data
when can you ignore an outlier?
if it is due to a measuring or recording error
what does cleaning data mean?
- identifying & either correcting or removing inaccurate data values (caused by recording or other errors) or extreme values
- removing units or other symbols from data
- deciding what to do about missing data
what can you use a control group to test?
the effectiveness of a treatment
what are matched pair tests?
- 2 groups of people are used to test the effects of a particular factor
- each individual is placed with another person from the other group who has everything in common with them except for the thing being studied
what is a hypothesis?
an idea that can be tested by collecting and analysing data
should a hypothesis be a statement or a question?
statement
when designing an investigation what factors do you need to consider?
- time
- cost
- ethical issues
- confidentiality
- convenience
- how to select your population & sample
- how to deal with non-response
- how to deal with unexpected response
