statistics exam 1 Flashcards
the basic unit of an experiment upon which the treatment is applied.
individual
An experimental condition where neither the subjects nor the diagnosticians (doctor, nurse, etc) know which treatment each subject received.
double blind
a weakness in experiments where the setting of the experiment does not realistically duplicate the conditions we really want to study.
lack of realism
an experimental design where all individuals are assigned at random to treatments
completely randomized
a study in which treatments are imposed on the individuals before responses are measured.
experiment
the grouping of individuals according to some similar characteristics. The random allocation is carried out separately within each group.
Blocking
A treatment where either no experimental condition or a placebo treatment is applied to the individuals in order to determine whether the active treatment works. This together with randomization enables the researcher to “control” lurking variables.
control
A study in which data are gathered without imposing treatments on the individuals.
observational study
A variable that is studied to determine whether it affects the outcomes of a study.
explanatory variable
A variable that has an effect on the response variable but is not included as one of the variables in a study.
lurking variable
the response of patients to any treatment that has no physical effect.
placebo effect
a method of assigning individuals to treatment groups that eliminates bias and gives each unit the same probability of being assigned to any treatment group.
randomization
results of a study that differ too much from what we expected because of randomization to attribute to chance.
statistically significant
a situation where the effect of one variable on the response variable cannot be separated from the effect of another variable on the response variable.
confounding
The application all the treatment combinations to more than one individual within an experiment
replication
Type of sampling required for inference.
sample selected with some type of random device
Using results from a sample to draw conclusions about the entire population.
inference
A sampling scheme where the population has been divided into strata according to some characteristic and a simple random sample is selected from each stratum.
stratified sample
A sample selected in such a way that the probability of each possible sample of size n has a known chance of being selected.
probability sample
A method of sample selection that consists of people choosing themselves by responding to a general appeal.
voluntary response sample
A condition that occurs when the design of a study systematically favors certain outcomes.
bias
The entire group of individuals about whom we desire to collect information.
population of interest
A subgroup of the population that we actually examine and about whom we gather information
sample
A sample of size n selected from the population in such a way that every possible sample of size n has an equally likely chance of being selected.
simple random sample
A sample type where the researcher contacts those subjects who are readily available and does not use any random selection.
convenience sample
An observation that falls outside the overall pattern of the data set.
outlier
measure for the center of the data that “balances” the data.
mean
a measure of the center of data that splits the ordered data in half.
median
A location measure of the data that has approximately one fourth or 25% of the data below it.
Q1
A location measure of the data that has approximately one fourth or 25% of the data above it.
Q3
s
sample standard deviation
r
correlation coefficient
n
sample size
A representative measure of the deviations of the data about the mean
standard deviation
maximum observation minus the minimum observation
range
A measure of the “average” or typical deviation of the observations about the mean.
standard deviation
The difference between the third quartile and the first quartile.
IQR, interquartile range
the measure of variability that should be used for strongly skewed data or data with outliers.
interquartile range
A curve that is mound shaped symmetric used to model data from measurements on animal species.
Normal Distribution
A normal distribution that has a mean of zero and a standard deviation of one.
standard normal distribution
A measure of the number of standard deviations of a value or observation from the mean.
z-score
In a normal distribution, the percentages of values that are within on e standard deviation of the mean.
68%
In a normal distribution, the percentage of values that are within two standard deviations of the mean.
95%
A graph for categorical data
bar graph
A plot of data that incorporates the maximum observation, the minimum observation, the first quartile, the second quartile, and the third quartile.
boxplot
A distribution where the left side of the distribution extends in a long tail.
left skewed
A list of the possible values of a variable together with the frequencies of each value.
distribution
The shape of a distribution where the mean exceeds the median.
right skewed
A plot used to provide a picture of one variable quantitative data.
stemplot, dotplot, histogram, or boxplot
The shape of a histogram where the median exceeds the mean.
left-skewed
The shape of a histogram where the mean equals the median.
symmetric
The recommended plot for displaying small quantitative data sets
stemplot
The preferred measures of spread and center for strongly skewed distributions or distributions with outliers.
median and interquartile range
