Chapter 1 Statistics Terms

statistics

the science of collecting, organizing, presenting, analyzing, and interpreting data.

descriptive statistics

methods for organizing, summarizing, and presenting data in an informative way.

inferential statistics

methods used to determine something about a population on the basis of a sample.

population

the entire set of objects or individuals of interest.

parameter

a summary measure for a population ex. the mean

statistic

a summary measure for a sample ex. the mean used as estimate for a population parameter

sample

a portion or part of the population of interest.

qualitative variables

a categorical variable, or an "attribute" ex. color of your hair, gender, race, what state you live in. things can be put into categories. (nominal and ordinal level data)

quantitative variables

variables who's value can be counted or measured ex. the number of students in a classroom, the outdoor temperature, the amount of gas in your car. (discrete or continuous?) (interval and ratio-level data)

discrete variables (quantitative)

quantitative variables that can assume only certain values and there are usually gaps between those values, also referred to as counts data. ex. the number of finance majors, the number of courses you are registered for.

continuous variables (quantitative)

quantitative variables that can assume any value within a given interval. Typically measured variables. ex. temperature in the room, speed of a car.

nominal level data (qualitative)

data variables that can only be categorized and counted. (lowest) ex. the state that you live in

ordinal level data (qualitative)

data that can be placed into categories and then the categories can be ordered. The orders may be according to the "best", "largest", or "most popular" for example. (low) ex. year in college (rankings are also in this category)

interval level data (quantitative)

measure that includes all the properties of ordinal data, but in addition, the difference between successive categories is consistent. (high) ex. temperature (only rises one degree at a time), shoe size (rises by half measurements)

ratio-level data (quantitative)

measure that includes all properties of interval data, but in addition, the 0 point is meaningful and therefore meaningful ratios can be formed. (highest) ex. the number of gallons of gas in your car (can be zero), the speed a car is traveling (can be zero)

occupation (teacher, attorney, engineer, etc.)

qualitative and nominal

your eye color

qualitative and nominal

car size (sub-compact, compact, midsize, or luxury)

qualitative and ordinal (can do by size largest to smallest)

length of time standing in line at the bookstore

quantitative and ratio and continuous (can assume any value)

number of rings before the call was picked up at a call center

quantitative and ratio and discrete (because can measure how many)

the number of accidents on 385 in July

quantitative and ratio and discrete (because can measure how many)

the amount of coffee in a large dunkin' donuts cup

quantitative and ratio and continuous (can assume any value)

mileage from your next tank of gas

quantitative and ratio and continuous (can assume any value)

rankings for the top 25 college football teams

qualitative and ordinal

points scored in a football game

quantitative and ratio and discrete

racial composition of a high school classroom

qualitative and nominal

heights of 15 year olds

quantitative and continuous

a kindergarten teacher marks whether each student is a boy or girl

nominal

a ski resort records the daily temperature during the month of January

interval

the restaurant surveys its customers about the quality of its waiting staff on a scale of 1 to 4, where 1 is poor and 4 is excellent.

ordinal

an investor collects data on the weekly closing price of gold throughout a year

ratio

a meteorologist records the amount of monthly rainfall over the past year

ratio

a sociologist notes the birth year of 50 people

interval

an investor monitors the daily stock price of BP following the 2010 oil disaster in the Gulf of Mexico

ratio

frequency distribution

a table of data showing the number (or frequency) of items in each of several non-overlapping classes. used for nominal and ordinal level data.

relative frequency distribution

they reflect the proportion of the total number of observations that fall into each category. calculated as frequency of the class divided by total frequency.