Statistics Chapter 1

Data

set of measurement taken on a set of individual units

Variable

any characteristic that is recorded for each case

Categorical (Qualitative)

variable divides the cases into groups or categories based on some quality

Quantitative

variable measures a quantity with numbers

Explanatory Variable

Predicts values

Response Variable

value being predicted

Population

includes all individual or objects of interest

Sample

all the cases that we have collected data on (a subset of the population)

Statistical Inference

the process of using data from a sample to gain information about the population

Sampling bias

occurs when the method of selecting a sample causes the sample to differ from the population in some relevant way. Sample is not representation of population.

Sampling

choose a colorful sample from a colorful population

Simple Random Sample

each unit of the population has the same chance of being selected, Regardless of the other units chosen for the sample

Voluntary Samples

compromised of whoever chooses to participate

Association

two variables are associated if values of one variable tend to be related to values of the other variable

Causation

two variables are casually associated if changing the value of the explanatory variable influences the value of the response variable

Confounding variables

a third variable that is associated with both the explanatory variable

Observational Study

study in which the researcher does not actively control the values of any variable, but simply observes the values as they naturally exist

Experiment

a study in which the researcher actively control one or more of the explanatory variables

Randomized Experiment

the explanatory variable for each unit is determined randomly, before the response variable is measured

Treatments

the different levels of the explanatory variables

Control Group

Comparison groups, when determining whether a treatment is effective

Placebo Effect

often, people will experience the effect they think should be experiencing, even if they aren’t actually receiving the treatment

Placebo

a fake treatment that resembles the active treatment as much as possible

Double-blinded

neither the participants or the researchers involved should know which treatment the patients are actually getting

Matched Pairs Experiment

give each treatment to each case, and just randomize the order in which treatments are received