Stats exam one vocab

Individual

objects described by a set of data (could be a animal, person, or thing)

Variable

any characteristic of a individual

what are the two types of variables?

Numerical and Categorical

Discrete (Numerical)

Not able to take all possible real numbers in a reasonable range

Continuous (Numerical)

Able to take all possible real numbers in a reasonable range

Categorical

any variable that is not numerical

Nominal (categorical)

no real value in the order of categories

Ordinal (categorical)

There is meaningful order among the categories

What graphs are used for categorical variables?

bar graphs and pie charts

What graphs are used for numerical variables?

Stem leaf plot and histrogram

How to find mean

add up all the numbers, then divide by how many numbers there are

Median

The midpoint of distribution, it is the sample size plus 1 divided by two

Is mean or median resistant?

The median is resistant because it will be the same no matter what. The mean is NOT resistant because it will change based on the numbers in the value set

Is standard deviation resistant?

The standard deviation is NOT resistant

First quartile

the median of the lower half of the data set

Third quartile

the median of the upper half of the data set

5 number summary

min, Q1, median, Q3, max

Are quartiles resistant measures?

Quartiles are resistant

Inner Quartile Range (IQR)

the distance between Q1 and Q3. To find it subtract Q3-Q1

1.5 IQR rule

used for identifying outliers: any values that are more than 1.5 times the IQR lower than the first quartile or higher than the third quartile are called outliers

Scatterplot

a graphed cluster of dots, each of which represents the values of two variables

Explanatory variables go on the X axis and Response variables go on the Y axis

What does correlation (r) measure?

Correlation measures the degree of relationship between two or more variables

what does r tell us?

Whether there is a linear relationship between two variables, what direction the relationship is (positive or negative), and how strong the relationship is.

R is not resistant
R is not affected in the changing of number of units

Population

the entire group of individuals we want to know about

Sample

a part of the population we actually collect information from

Parameter

a number that describes the population

Statistic

A number that can be computed from sample data without using any unknown parameters

Sampling design

describes exactly how to choose a sample from the population

Bias

the design of a statistical study is biased if it systematically favors a outcome

Convince sample

easy to reach

Voluntary response sample

voluntary by individual

simple random sample

n individual from a population chosen in a way so that every set of n individuals has an equal an equal chance of the sample n being selected

Inference

A conclusion reached on the basis of evidence and reasoning

Observational study

observes individuals and measures variables of interest but does not attempt to influence the responses

Experiment

deliberately oppose some type of treatment on individuals to influence their response

Response variable

measures an outcome of a study

explanatory variable

A variable that helps explain or influences changes in a response variable.

Terms for experiments

subjects, factors, treatments, statistical significance

Subjects

individuals studied in an experiment

Factors

explanatory variables of experiments

treatments

any specific experimental condition applied to the subjects

Random

if individual outcomes are uncertain but there is nonetheless a regular distribution of outcomes in a large number of repetitions

Probability

the portion of times the outcome would occur in a very long series of reptation

Sample space

the set of all possible outcomes

Event

a set of outcomes, it will be a subset of the sample space

Discrete vs. Continuous Variables

discrete variables will be a list in a sample space and its probabilities whereas continuous variables are on a density curve and will occur under the umbrella of a density curve