Terms  Definitions 

bimodal 
distributions with two modes

comparing distributions 
use backtoback stem, or histogram/dot with same scale and compare their shape, center, and spread

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

level 
the experimental values that are chosen for each factor

distribution 
describes how a quantitative variable behaves. Generally include shape, center, spread, & unusual features.

undercoverage 
some portion of the intended population is either unrepresented or underrepresented

range 
the maximum data value minus the minimum data value

histogram 
a display for quantitative data that uses adjacent bars to represent counts or percentages of values falling in each interval

principles of experimental design 
control, randomize, replicate, block

outliers 
values that fall outside the overall pattern of the data

multistage sampling 
sampling schemes that combine several different sampling methods at different stages

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

variance 
the standard deviation squared, it is a measure of spread

Confidence Interval 
Used to estimate the population parameter; an interval within which we believe lays the TRUE population parameter.

bar chart 
a display for categorical data that uses bar height to represent counts or percentages for each category

frequency table 
lists the categories for a categorical variable and displays the counts for each category

statistic 
a number that describes the data; it can be a measure of center or spread

5 number summary 
includes the minimum, first quartile, median, third quartile, & the maximum

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

Pvalue 
The chance of getting the results if the null hypothesis is true.

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

Theoretical Probability 
The proportion of times the outcome would occur in a very long series of repetitions (determined mathematically).

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

simple random sample 
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.

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

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

quantitative variable 
where the data collected is numerical and it makes sense to use it for numerical operations

measures of center 
mean for distributions that are symmetric, median for all other distribution shapes

modified boxplot 
a display for quantitative data that graphs the fivenumber summary on an axis and shows outliers of they exist

Interquartile Range (IQR) 
the third quartile minus the first quartile

dotplot 
a display for either kind of data that uses a dot to represent each individual in the data set

double blind 
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

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

Probability Model 
a list of all possible outcomes and the probability of each

Central Limit Theorem 
The sampling distribution of a large sample will be approximately normal even if the population is not normal.

Statistically significant 
When the pvalue is lowp; not likely to happen by chance is the null hupothesis is true.

Empirical Probability 
The number of times an outcome occurs in a set of trials that are actually performed (used as an estimate of the theoretical probability).

median 
the value in the center of an ordered data set

relative frequency table 
lists the categories for a categorical variable and displays the percenatges for each category

outlier formula 
less than Q1  1.5 (IQR)
more than Q3 + 1.5 (IQR) 
Sample Space 
a list of all possible outcomes of a random phenomenon S= {...........}

first quartile 
the value where 25 % of the data fall below it in an ordered list

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