©G Dear 2008, 2010 – Not to be sold/Free to use General Mathematics Preliminary Collecting Data Bias Stage 6 - Year 11 Press Ctrl-A ©G Dear 2008, 2010 – Not to be sold/Free to use

Statistics - Bias Bias happens when the survey results are affected by the poor choice in the sample. For Example: Asking women if there should be a female only gym. Expected Answer: Yes Asking men if there should be a male only gym. No! Expected Answer: Asking student if teachers should be paid more. Asking teachers if teacher should be paid more.

Statistics – Bias (Conscription) Yes Prime Minister Video How to make a balanced survey

Statistics - Bias (Conscription) Yes Prime Minister Video You know what happens: A nice young lady comes up to you. Obviously you want to create a good impression. You don't want to look a fool, do you? So she starts asking you some questions:

Statistics - Bias (Conscription) Mr. Woolley, are you worried about the number of young people without jobs? Yes Are you worried about the rise in crime among teenagers? Yes Do you think there is a lack of discipline in our Comprehensive schools? Yes Do you think young people welcome some authority and leadership in their lives? Yes Do you think they respond to a challenge? Yes Would you be in favour of reintroducing National Service? [Conscription] Yes

Statistics - Bias (Conscription) Mr. Woolley, are you worried about the danger of war? Yes Are you worried about the growth of armaments? Yes Do you think there is a danger in giving young people guns and teaching them how to kill? Yes Do you think it is wrong to force people to take up arms against their will? Yes Would you oppose the reintroduction of National Service [Conscription]? Yes

Do you like this pair of jeans? Do you like the Beatles music? Statistics - Bias You don’t like this pair of jeans do you? Should be Do you like this pair of jeans? You like the Beatles music, don’t you? Should be Do you like the Beatles music?

Statistics – Bias (Causes) 1. Undercoverage When some parts of the population are under represented. 2. Non-response A big problem in mail surveys. 3. Leading questions Getting the answer you want.