POSC 202A: Lecture 1 Introductions Syllabus R Homework #1: Get R installed on your laptop; read chapters 1-2 in Daalgard, 1 in Zuur, See syllabus for Moore and McCabe Today: why statistics? Where is the science?

Why Statistics?

Statistics: Uncertainty The world is stochastic, not deterministic.

Stochastic A process characterized by chance, randomness or probability. In other words…

Stochastic In other words…. SHIT HAPPENS!

Deterministic A theory holding that, in nature, social phenomena are causally determined by preceding events.

Statistics: Uncertainty Deterministic World ViewStochastic World View

Statistics: Uncertainty Deterministic World ViewStochastic World View The relationship between the cigarettes and death rate (i.e. the slope) is identical in both graphs.

Statistics: Uncertainty The world is stochastic, not deterministic. Statistics provides a framework that allows us to account for this uncertainty.

Statistics: Uncertainty The world is stochastic, not deterministic. Statistics provides a framework that allows us to account for this uncertainty. Statistics is about guessing, or drawing inference.

Statistics: Uncertainty Statistics provides a framework that allows us to account for this uncertainty. Statistics is about guessing, or drawing inference. But There are many ways to guess:

Statistics: Uncertainty Statistics provides a framework that allows us to explicitly account for uncertainty. We can estimate how confident we should be in our guesses.

Political Science Where is the science?

Political Science Where is the science? What make the study of politics scientific?

Political Science- Empirical study of the political world: the study of what is, not what should be.

What do political scientists do? Describe, classify and explain events relating to the political world.

What do political scientists do? Describe, classify and explain events relating to the political world. Try to distinguish the systematic from the non- systematic.

What do political scientists do? Describe, classify and explain events relating to the political world. More specifically We try to draw inference from what we see to what we do not.

What is Inference?

Inference Making statements about what we do not see from what we do see. Examples?

How? Develop and test hypotheses based on theory.

Hypothesis a relational statement between two or more variables that is theoretically plausible and empirically verifiable.

How? Develop and test hypotheses based on theory.

What is Theory? Explanations for how the world works based on experience and observation.

How? Develop and test hypotheses based on theory.

How do we test theories and hypotheses?

For each hypothesis we make a list of all of the implications we can think of.

Implication

Some event or occurrence that must be true if the theory is true.

Hypothesis testing: the mechanics

Hypothesis testing: the mechanics 1.Articulate a hypothesis

Hypothesis testing: the mechanics 1.Articulate a hypothesis 2.Identify its implications Make a list of all the things that must be true if the theory is true. As many as we can think of! 3. 4.

Hypothesis testing: the mechanics 1.Articulate a hypothesis 2.Identify its implications 3.Attempt to prove the implications stemming from theory false. 4.

Hypothesis testing: the mechanics 1.Articulate a hypothesis 2.Identify its implications 3.Attempt to prove the implications stemming from theory false. 4.Evaluate by looking at data

Data Empirical evidence-information about the state of the world.

The same research principles always apply whether our data are qualitative or quantitative

Types of Evidence Qualitative evidence: The collection and organization of evidence (data) using particular facts (or often cases). Quantitative evidence: The collection and organization of evidence (data) using numbers usually through statistics.

What Makes the Process Scientific?

What Makes the Process Scientific? 1.The goal is inference

What Makes the Process Scientific? The goal is inference: Scientific research is designed to make descriptive or explanatory generalizations on the basis of empirical information.

What Makes the Process Scientific? The goal is inference (2 types) Descriptive A generalization about the state of the world based on the small part that we see. Causal A generalization about how the world works based on the small part that we see.

What Makes the Process Scientific? 1.The goal is inference 2.The procedures are public

What Makes the Process Scientific? The procedures are public Scientific research uses explicit, codified and public methods to generate and analyze data whose reliability can therefore be assessed.

What Makes the Process Scientific? The procedures are public Scientific research uses explicit, codified and public methods to generate and analyze data whose reliability can therefore be assessed. Results should be replicable.

What Makes the Process Scientific? 1.The goal is inference 2.The procedures are public 3.The conclusions are uncertain

What Makes the Process Scientific? The conclusions are uncertain Inference is an imperfect process. Without an estimate of uncertainty a description of the world is not very meaningful.

What Makes the Process Scientific? Two types of uncertainty: Fundamental uncertainty: Uncertainty inherent in the relationship between two things. Estimation uncertainty: Uncertainty in our inference due to the methods we use to draw the inference.

What Makes the Process Scientific? Fundamental uncertainty: Uncertainty inherent in the relationship between two things. Example: Probability of getting lung cancer Smoker.34 Non-smoker.03 Not everyone who smokes gets lung cancer.

What Makes the Process Scientific? Two types of uncertainty: Fundamental uncertainty: Uncertainty inherent in the relationship between two things. Estimation uncertainty: Uncertainty in our inference due to the methods we use to draw the inference.

What Makes the Process Scientific? Estimation uncertainty: Uncertainty in our inference due to the methods we use to draw the inference. Example: public opinion poll The uncertainty in our estimates is a function of how large the sample is that we draw. Sample size (N) Margin of Error 10010% 4005% 9003%

What Makes the Process Scientific? 1.The goal is inference 2.The procedures are public 3.The conclusions are uncertain 4.The content of science is its (the) method

What Makes the Process Scientific? The content of science is its (the) method: Scientific research adheres to rules on which its validity depends. These rules can be applied to the study of any subject.

What Makes the Process Scientific? The content of science is its (the) method: Scientific research adheres to rules on which its validity depends. These rules can be applied to the study of any subject. The possible subjects to be studied are endless but the principles (rules) for studying them are not.