ap statistics reading quiz 4.2 and 4.3

what is the marginal distribution of a two way table

Entries in the "Total" row and "Total" column

example of common response

More firefighters are present at fires where more damage occurs. Presence of firefighters does not increase damage. Both the number of firefighters and the amount of damage are showing a common response to the severity of the fire.

if two variables have a strong positive association, then as one variable increases, the other variable also increases. Is it fair to say that an increase in one variable causes an increase in the other variable? Explain.

No, it is not fair to say that changes in one variable cause changes in the other. Both variables may be changing in response to some other variable. Example: Shoe size has a positive association with reading ability in elementary school. Increasing shoe size does not cause an increase in reading ability. Both shoe size and reading ability are increasing as a student ages. Both variables have a COMMON response to age.

define causation

Causation is when increases in x cause increases in y.

common response

Common response occurs when changes in both x and y are caused by a lurking variable z

example of causation

The best method of establishing causation is to conduct a carefully designed experiment in which the effects of possible lurking variables are controlled.

example of confounding

The confounded variables may be either explanatory variables or lurking variables.

example of a lurking variable

A group of college students think herbal tea can improve people's moods. They make weekly visits to a local nursing home, where they visit with the residents and serve them tea. The staff reports that the residents are more cheerful and healthy. Lurking variable could be the residents enjoy the attention and the companionship of the college students not the tea;.

define a lurking variable

A lurking variable is a variable that is not one of the explanatory or response variables in a study and yet may influence the interpretation of relationships among these variables.

how is conditional frequency calculated

The relative frequencies in the body of the table

confounding

Two variables are confounded when their effects on a response variable cannot be distinguished from each other.

Good evidence of causation requires:

a strong association that appears consistently in many studies, a clear explanation for the alleged causal link, and careful examination of possible lurking variables.

To analyze categorical data, use --------- or ---------- of individuals that fall into various categories.

counts, percents

what is a two way table?

examine the relationship between two categorical variables.