STA 210

Treatment

what is being "done" to the subjects. type of intervention.

Response Variable

A variable that measures the outcome of a study. Also known as the dependent variable.

Example: A study is performed to see if reading more produces a higher IQ (Identify the explanatory and response variable)

Explanatory: Reading. Response: IQ (Notice: when labeling the variables I did not assign quantities to them)

Sample

Part of the population we collect information from. - used to draw conclusion about the entire group.

Census

Sample survey that looks at the entire population. -problem with census: time consuming, money - expensive to do, supply.

Placebo Effect

real response to a fake treatment.

(In response to what is Confounding?) What does this mean?

you have A and B, one of them is causing C, but you can't distinguish between the two. I.E. it may appear that A causes C, but really it is B that causes C.

Population

entire group we are interested in studying.

About.... die in traffic accidents

43,000

Correlation vs. Causation

-Correlation: straight-line association between two things -> it is visual. -Causation: When one thing causes the other.

Experiments

-Deliberately imposes some treatment to the individuals in your study. -The purpose of an experiment is to study whether the treatment causes a change in the response of the individuals. -Give good evidence for cause and effect.

Observational Studies

-Observes individuals and measures variables of interest. -Hands off. -The purpose of an observational study is to describe some group or situation. -no evidence - you can't use it as evidence.

About... of Americans identify themselves as Latinos

14%

About... deaths are from AIDS

16,000

About... deaths are from homicides

17,000

About... Americans die each year

2.4 million

U.S. Population is about...

300 million

Each year about... babies are born in the U.S.

4 million

There are about... black americans

40 Million

Statistical Significance

A difference between treatments that is sufficiently large that it is unlikely to have occurred by chance alone.

Explain how slippery evidence affects human inference?

At first glance we infer one thing, but with further review we see something else is true.

Roughly 1 in 4 who die, die from... more or less

Cancer

Explain the difference between Correlation and Causation.

Correlation is a straight line association between two things, it is visual. Causation is when one thing causes the other.

Roughly 1 in 4 who die, die from...

Heart Disease

How are lurking variables related to Simpson's Paradox?

Lurking variables can cause Simpson's Paradox to occur. We need to split the table up by the lurking variable.

What is the link between a lurking variable and confounding?

Lurking variables cause confounding.

Correlation

Mutual or complementary relationship - a relationship where two or more things are mutual or complementary.

Simpson's Paradox

Occurs when an association between two variables is reversed upon observing a third variable. -In probability and statistics, Simpson's paradox is a paradox in which a correlation present in different groups is reversed when the groups are combined. -An association in sub-populations may be reversed in the population. It appears that two sets of data separately support a certain hypothesis, but, when considered together, they support the opposite hypothesis.

Negative Association

Points have a downward trend from left to right.

Positive Association

Points have an upward trend from left to right.

Randomization

Produces groups of units that should be similar in all aspects (or eliminates potential biases due to order in which treatments are administered).

Objects

Usually are described by a set or data. They could be: people, animals, ice cream flavors, plants, fish, car.

Lurking Variable

Variable not directly studied that can compromise your ability to attribute any changes in the response to a treatment.

Scatterplot

Visual way of assessing association, both direction and strength.

Correlation Coefficient

Way of summarizing the relationship you'd see between two variables that you could represent with a scatterplot.

Why is it important to critically read news articles, and why should we be careful about spreading information we are not confident about?

We need to critically read to make sure that what we are reading is true.

Subjects

What is being treated or studied.

What is Confounding?

When the effects of two variables on response can't be distinguishes (often causes by a lurking variable).

Explanatory Variable

a variable we think might cause changes in the response variable. Also known as the independent variable or predictor variable.

Categorical variables

anything you describe with quality. example: gender, make of a car, ice cream flavor.

Variables

any characteristic of an individual. -a variable can take on different values for different individuals.

Numerical variable

anything you describe with numbers. example: speed, age, price, number of elevators in a building.