Data ?

Data is the information which you have obtained(or have been given)

Types of Data

Data

Qualitative data Quantitative data ( non numerical, like colours) ( numerical, like no of people on a bus) There are two types of Quantitative data Continuous data Discrete data

Continuous DataDiscrete Data

• Continuous data is which could take all the possible values within a given range,e.g the height of a tree.

• Discrete data is which increases in steps( often whole numbers),e.g. the numbers of rooms in a building.

• Discrete data does not have to consist only whole numbers. For example the size of shoes is also a discrete data, and the sizes go up in halves.

Collecting Data

• Surveys• Censuses• SamplesWe need to design and criticise questions

relating to Questionnaires

Qualitative or QuantitativeContinuous or Discrete

• The height of a person Continuous• The number of children in a family Discrete• The colour of the shoes of people on a train Qualitative• The speed of a car Continuous

Questionnaires

• A questionnaire is a list of questions designed to collect data. There are two types of questions used in questionnaires

1. An open question is one that has no suggested answers.

2. A closed question is one that has a set of answers to choose from, usually in the form of response boxes.

Questionnaires

• It is important that information in the response boxes:

1. Does not overlap2. Covers all possible answers3. Relates to the questions4. Be answered quickly

Questionnaires

• A small carefully chosen number of people can be used to represent the population being surveyed. These chosen individuals are called a sample and investigation is called a sample survey,

• The sample must be representative of all the people being investigated. If it isn't, it is a biased.

Example

Well designed questionnaire1. Tick one box to indicate your age group

Under 21 21 to 30 31 to 40 41 to 50 Over 50

These are response boxes. The categories do not overlap

2.How often have you visited the dentist in the last 4 years? Tick one box

Never 1 or 2times 3 or 4 times 5 to 6 times More than 6 times

These options are specific, unlike often or sometimes

3. Do you agree or disagree that people who visit dentist regularly have fewer fillings in their teeth?

3. Do you agree or disagree that people who visit dentist regularly have fewer fillings in their teeth?

Agree DisagreeAgree and Disagree makes the question inbiased

Example

• Tom wants to find out how many DVDs people buy. He uses this question on a questionnaire.

How many DVDs do you buy? 1-5 5-10 10-15 15-20Write down three things wrong with this question.• The response boxes overlap• The response boxes do not cover all possible answers( 0 or more

than 20 DVDs)• There is no time period in which the DVDs are bought,e.g each

week or each month.

Representing data

We can represent data in different ways.1. Two way Tables2. Pictograms3. Bar charts4. Frequency polygons5. Pie charts

Averages and range

1. Mean, median, mode and range2. Stem and leaf diagrams3. Averages from table 1( discrete data)4. Averages from table 2 ( continuous data)5. Scatter graphs

Two -Way Tables

Year 7 Year 8 Year 9 Total

Vegetarian 14 22 25 61

Not vegetarian 72 63 54 189

Total 86 85 79 250

In total 250 students were surveyed

86 Year 7 students surveyed

61 vegetaria

n total

63 non-vegetarian in year 8

Worked Example

• The two way table shows some arrangement of 85 students. Complete the two-way table

School Lunch

Packed Lunch

Others Total

Female 21 13 47Male 5Total 40 85

Answer -Worked Example

• The two way table shows some arrangement of 85 students. Complete the two-way table

School Lunch

Packed Lunch

Others Total

Female 21 13 13 47Male 19 5 14 38Total 40 18 27 85