the science of collecting organizing and interpreting data
the data that describes or summarizes something.
the complete set of people or things being studied
a subsect of the population from which the raw data are obtained
specific characteristics of the population that a statistical study is designed to estimate.
are number or observations that summarize the raw data.
is a sample in which the relevant characteristics of the sample members match those of the population.
simple random sampling
we choose a sample of items in such a way that every sample of a given size has an equal chance of being selected
we use a simple system to choose the sample, such as selecting every 10th or every 50th member of the population.
we use a sample that is convenient to select, such as people who happen to be in the same classroom
we use this method when we ar concerned about differences among subgroups, or strata, within a population. we first identify the subgroups and then draw a simple random sample with in each subgroup. the total sample consists of all the samples from the individual subgroups.
if a study's design or conduct tends to favor certain results
researchers observe or measure characteristics of the sample members but do not attempt to influence or modify these characteristics
researchers apply a treatment to some or all of the sample members and then look to see whether the treatment has any effects.
in an experiment is the group of sample members who receive the treatment being tested.
is the group who do not receive the treatment being tested
lacks the active ingredient of a treatment being tested in a study, but is identical in appearance to the treatment.
refers to the sistuation in which patients imporve simply b/c they believe they are receiving a useful treatment.
if the participants do not know whether thay are members of the treatment group or members of the control group , but the experiments do know.
participants and experimenters do not know who belongs to the treatment group or control group.
margin of error
is used to describe a confidence interval that is likely to contain the tru population paramenter. We find this interval by subtracting and adding the margin of error from the sampl statistic obtained in the study. ie.from = sample stat - margin of error or to = sample stat + margin of error
occurs whenever researchers select their sample in a way that tends to make it unrepresentative of the population.
mostly happens with surveys and polls. when people choose to participate.
any item or quantity that can vary or take on different values. In statistics it is the items you seek to measure.
2 columns where one is frequency and the other is categories.
describes qualities or categories
represent counts or measures.
is a bar graph for quantitative data catefories. the bars have natural order and the bar widths have specific meaning.
shows the data value for each category as a dot and the dots are connected with lines.
is a histogram or line chart in which the horizontal axis represents time.
shows different data sets in a vertical stack.
exists between two variables when higher values of one variable consistently go with higher values of another or when higher values of one variable consistently go wieht lower values of another.
is a graph in which each point represents the values of two variables.
there is no apparent relationship between the two variables.
both variables tend to increase or decrease together
2 variables tend to change in opposite direction.
strength of correlation
the more closely 2 variables follow the general trend the stronger the correlation.