AP Statistics Unit 3

nobody can guess the outcome before it happens. when we want things to be fair, usually some underlying set of outcomes will be equally likely (although in many games, some combinations of outcomes are more likely than others).

mimics reality by using random numbers to represent the outcomes of real events.

the sequence of several components representing events that we are pretending will take place

trial's outcome

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

a representative subset of a population, examined in hope of learning about the population

when sampling methods either over or under emphasize some characteristic of the population

protects us from the influences of all the features of our population by making sure that, on average, the sample looks like the rest of the population.

the number of individuals in the sample that is important.

attempting to survey the entire population

mathematical measures taken from the entire population like the population mean and standard deviation

we want the statistics we compute from a sample to reflect the corresponding parameters accurately.

the random selection of subjects used to reduce bias in either surveys or experiments

mathematical measures taken from a sample of the population of interest like the sample mean and sample standard deviation

abbreviated SRS, this requires that every item in the population has an equal chance to be chosen and that every possible combination of items has an equal chance to exist. No grouping can be involved.

a list of individuals from which the sample is drawn

Samples drawn at random generally differ one from another. Each draw of random numbers selects different people for our sample. These differences lead to different values for the variables we measure

population is divided into homogenous groups and then a random sample is drawn from each group

population is split into parts or clusters usually based on geography and then entire clusters are selected randomly and sampled

sampling schemes that combine several different sampling methods at different stages

a sample is drawn from the population by following a systematic plan to give every object in the population an equal chance to be chosen but all possible groups can not be formed

a large group of individuals is invited to respond, and those who choose to respond are counted

The sample is not representative, even though every individual in the population may have been offered the chance to respond, which invalidates the survey.

a poor way to collect a sample - do what is convenient for the surveyor, data is usually very biased

some portion of the intended population is either unrepresented or under-represented

bias created when people who are randomly selected refuse to particiapte in the sample

anything in the survey design that influences the responses from the sample

an experimenter must identify at least one explanatory variable

The specific values that the experimenter chooses for a factor

The combination of specific levels from all the factors that an experimental unit receives

when our data values are not independent of one another and are related somehow to one subject - it is a form of blocking

a study based on data where no manipulation of factors has been employed, we simply observe what has or will happen

a study where there is a definite random assignment of subjects to treatments

the process, intervention, etc that is applied to each subject in an experiment

control, randomize, replicate, block

a group created the provide a basis for comparison usually either an old or placebo treatment

when the subjects in an experiment do not know if they are in the treatment or control group

when the subjects as well as those evaluating the result of an experiment do not know which subjects are in the treatment or control groups

a fake treatment often given to the control group to help prevent the placebo effect (subjects improving by the power of suggestion)

subjects or experimental units are grouped together homogeneously because of some charcteristic they have in common that is believed might effect the experiment

when the results of an experiment can be determined because a variable has not be accounted for and has interferred with your results

a study where we collect data as it happens

a study where we collect data from events that have happened in the past