##### QBA Exam 1

Data is

Information

Statistics is how data goes from being a bunch of numbers to being?

A conclusion

Descriptive statistics

procedures for organizing and summarizing data.

think: describe

What can descriptive statistics tell us?

What scores did we obtain?

are the scores generally high or low?

are the scores close together?

how does any one score compare to the others?

Inferential statistics

Procedures used to infer about a large group of people or items based on data collected from a small subset of this group

Population

complete set of events in which you are interested, usually quite big

Population parameter

Numerical values summarizing data population. Greek symbols

Sample

set of actual observations; subset of the population

sample statistics

numerical values summarizing sample data. english symbols

Why are population parameters difficult to calculate?

Cost prohibitions and the infeasibility of collecting data on the entire population

The teachers' union in California wants to know the average salary for high school teachers throughout the country. what is the teachers union presumably planning to calculate?

sample statistic

TIme series

data that is collected over a period of time

cross-sectional

data that is collected at the same point of time

variable

properties of objects/people that can take on different values

ex. age, political attitudes, geographic region, etc.

qualitative variables

data representing counts or numbers of observations in each category

ex. the # of males or females

quantitative

data obtained by measuring objects or events

ex. height, weight, money, time

continuous variable

variables that can take on any value. allows for fractional amounts or decimals.

ex. weight, time, age

discrete variables

variables that can take on only a small set of possible values.

ex. number of traffic tickets, gender

are nominal variables discrete or continuous?

discrete

what is an example of a continuous quantitative variable?

Time spent commuting to work

Measurement

assignment of numbers to data

nominal scales

numbers are used to distinguish among objects. the numbers have no meaning-- qualitative

ex. gender: male = 1, female= 2

Ordinal scales

numbers used to place objects in order along a continuum- rank order. No info about the differences between points on the scale, just info about relative order/rank

ex. your list of top 10 favorite movies

interval scales

scale where equal intervals between objects represent equal differences. can speak of differences between scale points. no true zero point, and ratios are not equal.

ex. the difference between 80 degrees and 40 degrees = the difference between 120 degrees and 80 degrees

ratio scales

same as interval but with a true zero/absolute point.

ex. height, weight, calories consumed, time, friends

ratios ARE meaningful