Statistics Ch. 1

32 terms

data

observations that have been collected

statistics

collection of methods for planning studies and experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclustions based on the data.

population

complete collection of all elements to be studied. Complete because it includes all subjects to be studied.

census

collection of data from EVERY member of population

sample

SUBCOLLECTION of members selected from a population

parameter

numerical measurement describing some characteristic of a POPULATION

statistic

numerical measurement describing some characteristic of a SAMPLE

quantitative data

consist of numbers representing counts or measurements

qualitative data

can be separated into different categories that are distinguished by some nonnumeric characteristic

discrete data

result when # of possible values is either a finite number or a "countable" number

continuous data

result from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interruptions or jumps.

nominal level of measurement

characterized by data that consist of names, labels, or categories only. Cannot be arranged in an ordering scheme.

ordinal level of measurement

can be arranged in some order, but differences between data values either cannot be determined or are meaningless.

interval level of measurement

like ordinal, but difference between any 2 data values is meaningful.

ratio level of measurement

interval level with additional property that there is also a natural zero starting point.

voluntary response sample

respondents themselves decide whether to be included

observational study

observe and measure specific characteristics but don't MODIFY subjects

experiment

apply some TREATMENT and then proceed to observe its effects on the subjects (experimental units)

cross-sectional study

data are observed, measured, and collected

retrospective study

data collected from the past by going back in time

prospective study

data collected in the future from groups sharing common factors

confounding

not able to distinguish among effects of different factors

placebo effect

when an untreated subject incorrectly believes that he/she is receiving a real treatment and reports an improvement in symptoms

blinding

subject doesn't know whether he/she is receiving a treatment or a placebo.

double-blind

blinding occured at 2 levels

random sample

members from population are selected in such a way that each INDIVIDUAL MEMBER has and equal chance of being selected

simple random sample

n subjects are selected so that every possible sample of the same size n has the same chance of being chosen

probability sample

selecting members from a population in a way that each member has a known chance of being selected.

systematic sampling

select a starting point then select every kth (10th, 50th, etc) element in the population

convenience sampling

use results that are easy to get

stratified sampling

subdivide the population into at least 2 different subgroups so that subjects within same subgroup share same characteristics

cluster sampling

divide population into sections then randomly select some of those clusters and then choose ALL members from selected clusters