Sampling & CLT
Parameter
A number that describes an entire population.
The true mean height of all students at a university.Terminology
Glossary
Sampling & CLT
Statistic
A number computed from a sample.
The mean height of 80 sampled students.Inference
P-value
The probability of results this extreme or more extreme, assuming the null hypothesis is true.
A p-value of 0.03 is evidence against H0 at alpha = 0.05.Inference
Confidence Level
The long-run success rate of a confidence interval procedure.
A 95% method captures the true parameter in about 95% of repeated samples.Inference
Type I Error
Rejecting the null hypothesis when it is actually true.
The significance level alpha is the Type I error rate.Inference
Type II Error
Failing to reject the null hypothesis when the alternative hypothesis is true.
A false negative in a hypothesis test is a Type II error.Inference
Power
The probability of rejecting the null hypothesis when it is false.
Power equals 1 - beta, where beta is the Type II error probability.Regression & Correlation
Residual
The observed value minus the predicted value.
If y = 12 and yhat = 9, the residual is 3.Sampling & CLT
Standard Error
The standard deviation of a statistic across repeated samples.
The standard error of xbar is sigma divided by sqrt(n).Descriptive Statistics
Outlier
A data point that is unusually far from the rest of the data.
In 2, 4, 5, 6, 50, the value 50 is a likely outlier.Probability Foundations
Independence
Two events are independent when one occurring does not change the probability of the other.
Two separate fair coin flips are independent.