stats vocab

unbiased sample

A sample in which all members of the population of interest are equally likely to be included (usually through some random method), and therefore the results can generalize to the population of interest.

Sample

part of a population

stratified sample

the population is divided into strata and a random sample is taken from each stratum

cluster sampling

Divide the population area into sections (or clusters). Then randomly select some of those clusters. Now choose all members from selected clusters.

systematic sampling

A procedure in which the selected sampling units are spaced regularly throughout the population; that is, every n'th unit is selected.(like every 25th person being sampled)

Census

A complete enumeration of a population.

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion

simple random sample

A sample of size n selected from the population in such a way that each possible sample of size n has an equal chance of being selected.

Randomization

the best defense against bias, in which each individual is given a fair, random chance of selection

population parameter

a numerical measure that describes an aspect of a population.There are many population parameters. For example, the population size (N) is one parameter, and the mean diastolic blood pressure or the mean body weight of a population would be other parameters that relate to continuous variables.

sample statistics

A sample statistic (or just statistic) is defined as any number computed from your sample data. Examples include the sample average, median, sample standard deviation, and percentiles.

Representative

this kind of sample accurately reproduces the characteristics of the population a researcher is studying

sampling frame

a list of individuals from whom the sample is drawn.Indivuals who may be the population of interest ,but who are not in the sampling dram cannot be included in any sample.

multistage sampling

Use a variety of sampling methods to create successively smaller groups at each stage. The final sample consists of clusters. (using multiple methods of sampling)

pilot survey

A small scale replica of a survey done to find out if the main survey will work

voluntary response bias

bias introduced to a sample when individuals can choose on their own whether to participate in the sample

convience sample

A sample which consists of members of a population that are easily accessed. They often fail to representative because not every individual is equally available.

Undercoverage

a sampling scheme that biases the sample in a way that gives a part of the population less representation than it has in the population

non responsive bias

bias caused by those who would be in the sample,but can't be contacted or refuse to answer

response bias

conditions or factors that take place during the process of responding to surveys, affecting the way responses are provided. Such circumstances lead to a nonrandom deviation of the answers from their true value.

Bias

any systematic failure of a sampling method to represent its population( relying on voluntary response, undercoverage ,nonresponse bias,)

Population

The entire group of individuals or instances about whom we hope to learn.

sample survey

a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population

sample size

the number of individuals in a sample

sample variability

sample to sample differences

simulation

an imitation of a possible situation

trial

each repetition or observation of an experiment

random

An outcome is random if we know the possible values it can have, but not which particular value it takes.

Generating Random Numbers

Random numbers are hard to generate. Nevertheless, several internet sites offer an unlimited supply of equally likely random values.

Simulation component

A component uses equally likely random digits to model simple random occurrences whose outcomes may not be equally likely.

response variable

A variable that measures an outcome of a study.

cofounding variable

a factor other than the independent variable that might produce an effect in an experiment (starting weight affecting both exercise and blood pressure and blood pressure being dependent on exercise.

question wording bias

When a question leads a person to give a specific or untruthful answer.

observational study

a study based on data in which no manipulation of factors has been employed

Variability

in a set of numbers, how widely dispersed the values are from each other and from the mean