Statistics Basics: Unit 2 Flashcards

statistics

collecting data, analyzing it, and making decisions about it

descriptive statistics

• “describes”

• consists of methods for organizing / summarizing data

• includes the construction of graphs, charts, and tables

• includes the calculation of various descriptive measures such as averages, measures of variation, and percentages

inferential statistics

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

• infer, estimates, predict(ion(s)), sample

population

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

sample

that part of a population from which information is obtained

parameter

describes a population

statistic

describes a sample

interrelation

use the techniques of descriptive stats to organize and summarize the info obtained from a sample before carrying out an inferential status

qualitative data

refers to observations that are attributes

• ex: gender, eye color, blood type, etc. (words and letters)

quantitative data

refers to observations that are numerical

• ex: height of a student, percentage of seniors with college grants, etc. (numbers)

discrete numerical data

results from a count (often whole numbers)

• ex: the number of students in a class

continuous numerical data

results from the measure of a quantity (often decimals)

• ex: temperature, length, time, weight, mean, etc.

grouping

one of the most common methods of organizing data (allows a complicated set of data to be compact and easier to understand)

classes

categories of grouping data

observations

data pieces

frequency

the number of observations that fall in a class

relative frequency

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

grouped-data table

a table that provides the classes, frequencies, and relative frequencies for a set of data (describes the frequency and relative frequency distributions of the data set)

lower cutpoint

the smallest value that could go in a cutpoint grouping class

upper cutpoint

the smallest value that could go in the next higher cutpoint grouping class

width

the difference between upper and lower cut points of class

midpoint

the middle of a quantitative class, obtained by taking the average of its lower and upper cutpoints

← symbol means:

“up to, but not including” or “-under”

statistics started in the:

20th century

author who wrote the first stats book → “Book of Mortality”

John Grant

man who started probability

Jerome Cardan

misleading statistics

graphs and statistics are often used to persuade advertisers and others; may accidentally or intentionally present info in a misleading way

• ex: art is often used to make a graph more interesting, but it can distort the info

common misleading stats situations:

• biased sampling

• sample too small

• comparing non-comparable groups

• “more / higher / better than what?”

• “If B follows A, then A caused B.”

• graph scaling

• assuming a trend will continue without changing