Intro to Statistical Inference - Test 1

Descriptive statistics

methods for organizing and summarizing information

Population

the collection of all individuals or items under consideration in a statistical study

Sample

part of the population from which information is obtained

Inference statistics

methods for drawing and measuring the reliability of conclusions about a population based on information obtained from a sample of the population

observational study

researchers observe characteristics and take measurements

designed experiement

researchers impose treatments and controls

census

obtaining information on the entire population

representative sample

closely reflect the relevant characteristics of the population under consideration

probability sample

using a random device to decide which members of the population will constitute the sample

simple random sampling

a sampling procedure for which each possible sample of a given size is equally likely to be the one obtained

variables

a characteristic that varies from one person or thing to another

qualitative variable

a nonnumerically valued variable

quantitative variable

a numerically valued variable

discrete variable

a quantitative variable where all possible values can be listed

continuous variable

a quantitative variable whose possible values form some interval of numbers

frequency

the number of times of a particular value occurs

frequency distribution

a listing of all values and their frequencies

relative frequency

the ratio of the frequency of a value to the total number of observations

pie chart

a disk divided into wedge-shapes that are proportional to the relative frequencies

bar chart

displays the distinct values of the data on a horizontal axis and the relative frequencies or frequencies on a vertical axis

Guidelines for classes

the number of classes should be small enough to provide an effective summary but large enough to display the relevant characteristics of the data

single value grouping

classes that represent a single possible value

limit grouping

classes that represent a range of values

cut point grouping

classes that represent a range of values with labels such as "under"

histogram

displays the values on a horizontal axis and the frequencies of those classes on a vertical axis, the bars touch

dotplots

show the relative positions of the data

stem and leaf plot

a table that organizes quantitative data by separating each number into a stem (the leading digit or digits) and a leaf (the last digit)

distribution

provides the values of the observations and how often they occur

modality

the number of peaks or highest point

symmetry

whether it can be divided into 2 pieces that are mirror images

skewness

a unimodal graph that is not symmetric but skewed

population distribution

distribution of population data

sample distribution

distribution of sample data

truncated graph

a graph where the vertical axis doesn't start at 0

linear regression

used methods for examining the relationship between quantitative variable and for making predictions

scatter plot

a graph of data from two quantitative variables of a population

ŷ

y hat; predicted value of Y