Form and source of data
- Every piece of data in psychology carries two labels: one for its form and one for its source.
- Data in the form of numbers is quantitative, and data in the form of words is qualitative.
- Data the researcher collected is primary, and data someone else collected is secondary.
- The two labels are independent, so a set of interview quotes taken from a published study is qualitative and secondary at the same time.
Key Idea
- Two separate questions decide the label: one about whether the data is numbers or words and one about who collected it.
- Neither form is the better one, since a mean of 13.6 words tells you how much was recalled and a pupil's sentence tells you how they did it.
- One study can carry all four labels at once, so six classmates' sleep figures can sit next to published NHS guidance in the same write-up.
Quantitative data
Definition
Quantitative data
Data in the form of numbers, such as test scores, reaction times or how many people gave each answer, which is quick to summarise and easy to compare.
- Quantitative data is numerical, such as reaction times in milliseconds, recall scores out of 20, or the number of words remembered.
- Its strength is that it can be counted, compared between two groups, and put straight into a mean or a bar chart.
- A rating scale counts as quantitative, because a mood rated 7 out of 10 is a number.
- A score leaves out the reason behind the behaviour, so 9 words out of 20 does not say why the other 11 were lost.
Note
- A number can be counted without being accurate, so a mood rated 7 out of 10 is quantitative whether or not it matches how the person felt.
- Counting how many people mentioned a theme turns qualitative material into quantitative data, so the two forms are not sealed off from each other.
Qualitative data
Definition
Qualitative data
Data in the form of words, such as what someone says in an interview, which gives detail about how people think and feel but is harder to compare.
- Qualitative data is descriptive, such as interview quotes, written diary entries and notes on how a participant behaved.
- Its strength is the detail it gives about why someone behaved as they did.
- It is read for themes, with a quotation given to show each theme.
- Words cannot be averaged, and summarising them takes judgement, so two researchers can reach different themes.
Example
- A Year 11 class runs a memory practical, and five pupils recall 12, 15, 9, 18 and 14 words out of 20.
- Those five scores are quantitative, so they total 68 and give a mean of 13.6 words.
- After the test one pupil writes, "I chanted the words under my breath to keep them in my head", and that sentence is qualitative.
- The scores give 18 words as the top result, and the quotation gives a reason for it.
Primary data
Definition
Primary data
Data a researcher collects first-hand for their own study, for example by running their own experiment, questionnaire or observation.
- Primary data is collected first-hand for the study in question, such as timing your own participants or running your own questionnaire.
- Its strength is that it fits the aim exactly, because the collection was designed around that aim.
- The researcher knows how it was gathered, so its reliability can be judged directly.
- Collecting it takes time, so the sample is usually small.
Common Mistake
- The source and the form are two separate labels, because primary and secondary data can each be quantitative or qualitative.
- Numbers are not automatically the stronger choice, because one quotation can explain a result that a column of scores cannot.
Secondary data
Definition
Secondary data
Data that already exists because someone else collected it, such as official statistics, past studies or records.
- Secondary data has already been gathered by someone else, such as official statistics, past studies and school records.
- Its strength is speed and cost, because the collecting is done and the sample is often far larger than one researcher could reach.
- It was collected for someone else's purpose, so it may define its terms differently or come from a different group of people.
- Who collected it, when, and from whom are all checked before it is used, because old or unrelated figures can mislead.
Example
- A student wants to know how much sleep Year 11 pupils get each night.
- For primary data she asks six classmates, who report 7, 6, 8, 7, 5 and 9 hours.
- The total is 42 hours, so the mean is 42 divided by 6, which is 7 hours.
- For secondary data she uses NHS guidance that teenagers need eight to ten hours a night.
- Setting her mean of 7 hours against that guidance shows her classmates sleep less than the recommended amount.
Choosing the type of data
- Quantitative data fits an aim that needs groups compared, a mean calculated or a graph drawn.
- Qualitative data fits an aim that needs depth and the reasons behind a behaviour.
- Primary data fits an aim that no existing dataset matches closely enough.
- Secondary data fits a study with little time or money, or one that needs a larger picture than one researcher could gather.
- One study can use all four, setting a small primary sample of scores against a published figure, as the sleep example does.
Note
- Data becomes secondary once it is reused for a different question, so a researcher's own figures from an earlier project count as secondary here.
- A published mean cannot be recalculated without the original scores, so secondary data usually has to be taken as it was reported.
Turning this into marks
- When a type of data and a strength are both asked for, keep them as two separate points, one naming the type and one naming what it lets the researcher do.
- Give the form and the source as separate labels, so borrowed interview quotes are qualitative and secondary.
- Name the actual data in the study, such as words recalled out of 20, because "numbers" does not secure the knowledge mark.
- The mark most often lost is quoting a mean without its units, so write 13.6 words rather than 13.6.
Self review
- Define quantitative data and qualitative data in one sentence each.
- Give one strength of quantitative data and one strength of qualitative data.
- Is a mood rated 7 out of 10 quantitative or qualitative?
- Are published government crime statistics primary or secondary data, and what is one strength of using them?
- A student records classmates' sleep as 7, 6, 8, 7, 5 and 9 hours, so is that primary or secondary data, and what is the mean?
