Two kinds of data from one investigation

1. A class investigates whether pupils who revise for longer feel more confident walking into a test.
2. Their questionnaire asks how many minutes each pupil revised, asks them to rate their confidence out of 10, and then asks them to describe how they felt.
3. Two of those three questions produce numbers and the third produces words, so one questionnaire yields both types of data.

What quantitative data is

1. Quantitative data is numerical, and the word itself comes from quantity, so think of anything you can count or measure.
2. Reaction times in seconds, the number of words recalled, a mark out of 20 and a rating on a scale are all quantitative.
3. Closed questions, which give people a fixed set of answers to choose from, produce quantitative data.

What qualitative data is

1. Qualitative data is descriptive, and the word comes from quality, so think of detail and meaning rather than amount.
2. Interview answers, diary entries, written explanations and notes describing how someone behaved are all qualitative.
3. Open questions, which let people answer in their own words, produce qualitative data.

Strengths and weaknesses of quantitative data

1. One strength is that it is quick to analyse, because you can total it, average it and put it straight into a chart.
2. A second strength is that it is objective, because a rating of 6 reads as a 6 to whoever picks up the sheet, so the findings can be checked.
3. One weakness is that it tells you what happened but never why, since a confidence rating of 3 does not reveal whether the pupil was tired, unprepared or anxious.
4. A second weakness is that a fixed scale strips out meaning, because two pupils who both circle 6 may mean quite different things.

Strengths and weaknesses of qualitative data

1. One strength is that it carries rich detail about reasons, so you understand the thinking behind a behaviour rather than only its size.
2. A second strength is that it can turn up explanations you never thought to ask about, which a fixed scale could never collect.
3. One weakness is that it is hard to summarise and compare, because you cannot average thirty pages of answers.
4. A second weakness is that analysing it is subjective, since two researchers reading the same interview may pull out different themes.

Choosing which type to collect

1. Choose quantitative data when your question is about comparing groups, spotting a trend or drawing a graph.
2. Choose qualitative data when your question is about reasons, feelings or an experience nobody has mapped out yet.
3. Collecting both is often the strongest design, because the numbers show the size of an effect and the words explain where it came from.
4. In this investigation the ratings show that the pupil who revised longest also felt most confident, and the written answers explain why one pupil's confidence collapsed at the first question.

Turning this into marks

1. Name the type of data and give the reason, since both parts are asked for.
2. Pair every strength or weakness with what it does to the study.
3. The mark most often lost comes from writing about only one type when the question names both.