This measure of spread is resistant to extreme values.
IQR
This statistic measures the strength and direction of a linear relationship.
r (correlation)
This sampling method selects individuals who are easiest for researchers to reach.
Convenience sampling
This rule computes P(A or B) when the two events overlap.
P(A)+P(B)–P(A and B)
This value is the mean of the sampling distribution of sample means.
μ
This measure of center is pulled in the direction of skew.
Mean
This quantity represents the proportion of variation in y explained by x in a regression.
r²
This feature of experiments allows researchers to infer cause and effect.
Random assignment
This condition defines independence between events A and B.
P(A | B) = P(A)
This quantity is the standard deviation of the sampling distribution of xˉ\bar{x}xˉ.
σ/√n
This distribution shape is suggested when the mean is larger than the median.
Right-skewed
This value is computed as observed minus predicted.
Residual
This experimental design strategy groups subjects by a variable that affects the response before randomizing treatment.
Blocking
This formula is used to calculate the expected value of a discrete random variable.
Σ(x·p)
These two conditions establish when the sampling distribution of p^\hat{p}p^ is approximately normal.
np ≥ 10 and n(1–p) ≥ 10
These data points dramatically change the slope of a regression line when included.
Influential points
This transformation is often used to linearize exponential relationships.
Taking the log of y
This type of variable influences both the explanatory and response variables, creating a misleading association.
Lurking (Confounding) variable
This is what happens to the variance of X when it is multiplied by a constant a.
It becomes a²Var(X)
This formula gives the standard deviation of the sampling distribution of a sample proportion.
√[p(1–p)/n]
This rule identifies outliers using Q1, Q3, and a multiple of the IQR.
1.5×IQR rule
This term refers to predicting a response for an x-value outside the observed data range.
Extrapolation
This sampling method divides the population into homogeneous groups and samples from each group.
Stratified random sampling
This is the variance of X – Y when X and Y are independent random variables.
Var(X)+Var(Y)
This theorem explains why the distribution of sample means becomes approximately normal as n increases.
Central Limit Theorem