Chapter 1
places an individual into one of several groups or category
Categorical Variable
the standardized value that describes what fractional part of a standard deviation a value is from its mean
z-score
measures the direction and strength of the linear relationship between two quantitative variables
correlation
Choosing individuals who are easiest to reach
convenience sample
occurs when some groups in the population are left out of the process of choosing the sample.
Undercoverage
numerical values for which it makes sense to find an average
Quantitative Variable
in a normal distribution it shows that 68-95-99.7 percent of the data is within 1, 2 and 3 standard deviations
Empirical Rule
The difference between the observed and the predicted values of y
Residual
consists of people who choose themselves by responding to a general appeal
Voluntary Response Sample
occurs when an individual chosen for the sample can’t be contacted or refuses to participate.
Nonresponse
the distance between the 3rd and 1st quartiles
Interquartile Range
a distribution of the values that fall a certain percent below this given value
Percentile
a scatterplot of the residuals against the explanatory variable used to determine if the regression line fits the data
residual plot
that receives an inactive treatment or an existing baseline treatment
Control group
is a group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments
Block
tells us what value a variable takes and how often it takes these values
Distribution
Table used to find the percent of data under the curve after converting a number into a z-score
Standard normal table
The variables that may help explain or influence changes in a response variable (x)
explanatory variable
neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received.
Double Blind Experiment
An observed effect so large that it would rarely occur by chance.
Statistically significant
displays the percent of times a variable occurs
Relative Frequency Table
a scatterplot of the z-scores against the explanatory variable that is used to suggest that the data is norma
Normal Probability Plot
The use of the regression line outside the range of the data from which it was calculated
extrapolation
the random assignment of experimental units to treatments is carried out separately within each block.
Randomized Block Design
Use enough experimental units in each group so that any differences in the effects of the treatments can be distinguished from chance differences between the groups.
Replication