Key GCSE Statistics NotesPrimary Data:Data collected by person going to use it.

Advantage: Accuracy knownDisadvantage: Time consuming

Secondary DataData not collected by the person going to use it.

Advantage: Easy to get/CheapDisadvantage: Accuracy unknown

Key GCSE Statistics NotesPopulation:Everybody or everything that could be involved in the investigation.

Census:Data about every member of the populationAdvantage: Unbiased/AccurateDisadvantage: Time consuming

Key GCSE Statistics NotesSample:Only part of the population used in an investigation.

Advantage: Less Time/Cheaper/EasierDisadvantage: Possibly biased

Key GCSE Statistics NotesInterview:

Advantage: Detailed answers/Lots of questions askedDisadvantage: Expensive

Questionnaire

Advantage: CheaperDisadvantage: Answers less detailed

Possible poor response rate

Key GCSE Statistics NotesPilot Survey:A small scale of the questionnaire to be used

Advantage: Shows you likely responses

Checks questions are suitable

Allows you to tweak/alter /add questions if needed

Types of Data:

Quantitative variables: Qualitative variables:

These have numerical observations, such as

shoe size (7, 8, 9, 7.5, 8.5)

Height (178cm, 1.9m) and weight.

Variables that have non-numerical observations, eg. Eye colour,

Favourite food

Quantitative or Qualitative data

Which data is quantitative and which is qualitative?

1. Favourite colour

2. the amount of people in a class

3. the men's 100m sprint record time

4. The make of different cars

5. the capacity of a car's petrol tank

6. the gender of students in a class

7. the names of places visited

8. your age

9. your favourite food

10. car registration plates

Answers

1. qualitative

2. quantitative

3. quantitative

4. qualitative

5. quantitative

6. qualitative

7. qualitative

8. quantitative

9. qualitative

10. qualitative

Quantitative variables can be broken down further.

Quantitative variables:

Continuous data Discrete data

…Are measured on a scale and can take any value eg. height

The units of measurement (eg. CDs) cannot be split up; there is nothing between 1 CD and 2 CDs.

Statistics

Decide whether or not the following are continuous or discrete:

a) Shoe size:

b) Gender:

c) The numbers of chocolates in a box:

d) Times taken for athletes to run 100m:

Discrete because can only take specific values, eg, 7, 8, 8.5. Cannot get a size 8.35

Discrete because can only be male or female.

Discrete.

Time is continuous

Discrete and continuous data

Which data is discrete and which is continuous?

1. the number of pages in a book

2. the amount of people in a class

3. the men's 100m sprint record time

4. the number of Smarties in a tube

5. the capacity of a car's petrol tank

6. the length of your shoe

7. the number of hairs on your head

8. your age

9. the temperature in Timbuktu

10. your shoe size

Answers

1. discrete

2. discrete

3. continuous

4. discrete

5. continuous

6. continuous

7. discrete

8. continuous

9. continuous

10. discrete