Philosophy 1102 1st edition Lecture 11Outline of last lecturel. Standard Deviationll. Dividing curve lll. The size of standard deviation lV. How to calculate standard deviationV. What if results are skewed?Vl. The misuse of statistics Outline of current lecture Vll. Graphs and Pictograms Vlll. The post hoc fallacy again Current lecture Vll. Graphs and Pictograms A. Graphs and pictograms can be useful and instructive way of representing statistical data. B. But they also present “ opportunity” to misrepresent the statistical data. C. How the data is represented graphically is always a choice: some ways to do so can be significantly misleading. Vlll. The post hoc fallacy againA. Pure Chance During the last two months our football team was defeated in every game. In each game, the cheerleaders wore blue ribbons in their hair. Therefore, to avoid any further defeats, the cheerleaders should get rid of their blue ribbons. - A correlation can exist between two types of events by pure chance. - Correlation by pure chance are exploited by companies for advertisement purpose with very convincing, but misleading effectsOur toothpaste is more effective against cavities than our main competitor’s Tests have shown that among a group of randomly chosen people, twice as many people had activities who use our main competitor’s toothpaste compared to people using our toothpaste. - Pick small sample size (say, 10 people), do the study 100 times, discard the 99 studies that do not have the desired outcome. B. Common causePeter wakes up with a fever one morning. Around noon, he finds red spots on his skin. He concludes that his high body temperatures caused the red spots. - The red spots are not caused by the fever, but rather both the fever and the spots have a common cause: some infection. - There will be a correlation between two events, A and B, if both events are caused by the same third event, C.Philosophy 1102 1st edition - Recall the example of the drop in atmospheric pressure causing both a storm and the barometer to drop. For several weeks this July, we have seen leaves from the surrounding trees floating on the river. Shortly after, many dead fish could be seen floating between the leaves. The leaves in the water must have killed fish. - It’s more likely that there is a common cause for the trees shedding their leaves and the fish dying- perhaps some chemical