Statistics is concerned with the proper methods used to collect, analyse, present and interpret DATA There are two types of Statistics: Descriptive – any method used to display large amounts of information (eg) bar charts, pie charts, mean etc Inferential – when a statistician tries to predict, guess or forecast an outcome (eg) elections, weather

 Population – the entire group being studied  Sample – a group selected from the population in order to gather information  Data – any unordered list  Information – when a list is given order in some form or another  Variable –a characteristic being recorded or particular element of interest from a sample or population  Observation – the value of a variable for one element of a sample or population  Data Set – all the observations of a particular variable for the elements of the sample.  Census - a collection of DATA relating to a population  Sampling Frame – list of every item in a population  Random Sample – is a sample in which every member of the population has an equal chance of being selected  Statistical Inference – any conclusions drawn from a sample can then be applied to the whole population. NB avoid bias

Categorical qualitative – cannot be measured Numerical quantitive – can be measured Categorical Data – some questions cannot be answered with numbers  Colour of eyes, hair  Fav. soccer team, actor, etc  Grade in exam  Social class  Blood type  Where a person lives  Pain level Numerical Data – questions that are answered with numbers  People employed in manufacturing industry  Emigrants in 2009  Houses built in 2007  Temperature in Dubai in May  Average rainfall in Cork in Feb.  Time taken to run 100m in Olympics

Ordinal Categorical Data This is where the categorical data can be put in some order.  Exam grades – A, B, C, D, E  Stress levels – high, medium, low  Social class – lower, middle, upper  Restaurant service – poor, good, excellent  Pain level – none, low, moderate, severe Nominal Categorical Data This is where the categorical data cannot be put in order.  Fav. Colour  Colour of eyes, hair  Fav. Band  County of residence  Blood type

Continuous Numerical Data Data which is measured on some scale and can take any value on that scale – infinite number of values in the scale  Time spent on Facebook  Height  Arm span  Weights of students in Junior Cert. Discrete Numerical Data Numbers or measurements that can only have specific values, usually from counting – limited/finite  Shoe size  Family size  No. of planes landing in Cork on a particular day

There are two main sources of DATA : Primary and Secondary  Primary Data – is any Data collected by or for the person using it. The person collecting the data is the one that organises the method of collecting. ◦ Observational Studies – this is where the data is collected by making observations. The data is collected by counting, measuring or noting things that happen. They can include CASE-CONTROL studies. This is where you have two groups, one group is the CASE and the other is the CONTROL. Researchers will study the differences in the CASE?CONTROL groups. (eg) Medicine – compare two groups of people. The first group are known as the CASE and have a certain disease. The second group are known as the CONTROL and don’t have the disease. Researchers will then compare lifestyles etc of each group to try and learn the causes of the condition. These are laborious and time consuming and the researcher does NOT influence the responses ◦ Traffic survey might see how many vehicles pass over a bridge... NB. Very famous CASE-CONTROL study in 1950 done by Austin Hill and Richard Doll established link between lung cancer and smoking

Designed Experiments : in a designed experiment the researcher will apply some treatment to the subjects and then observe the effects the treatment has on the subjects. Data is collected by counting or measuring. (eg) Pharmaceutical companies carry out designed experiments when testing out a new drug. The drug is called an EXPLANATORY variable and the effect caused by the drug is called the RESPONSE variable. SECONDARY DATA  This is data that is not collected by the person that is going to use it.  Data can be found on the internet, newspapers, books, historical records, archives and databases.  Guinness Book of Records  Census of Population  Central Statistics Office  Census at Schools

Univariate Data This is where one item of information is collected from each member of a group.  Height in cms  Eye colour  Number of siblings Bivariate Data This is where two pieces of information are collected. (eg) a persons heoght and weight- paired data  Starting salary and years in education  Hair colour and gender  Amt of milk and number of eggs to make scrambled eggs  Number of people in a house and the number of rooms in the house

reliability Bias  Sample must be large enough –a correct representation of the population  The sample must be a randon selection from the population  Everybody has an equal chance of being selected –avoid BIAS  That there is as high a response rate as possible Bias is anything that might distort the data so that there will not be a correct representation from the sample.  Failing to identify correct population  Sample size is too small  Careless or dishonest questions  Misleading or ambiguous questions  Failure to get responses  Errors in recording the dat a  Data can go out of date- opinion poll conclusions can change over time