## Critical

The following symbols (ordered approximately as they were introduced) are CRITICAL to doing well in this course. You will be expected to know these on an instant recall basis.

Symbol Definition
n
Sample size.
$$\bar{\textrm{x}}$$
Sample mean (average) of the X variable.
s
Sample standard deviation.
μ
Population mean.
σ
Population standard deviation.
X~N(μ,σ)
The variable X is normally distributed with a mean of μ and standard deviation of σ.
H0
The null hypothesis.
HA
The alternative hypothesis.
α
The rejection criterion OR probability of making a Type I error.

## Important

The following symbols will be used often during the course and will be parts of multiple choice questions on quizzes. You will need to know these symbols to do well in this course.

Symbol Definition
Q1
First quartile.
Q3
Third quartile.
IQR
Interquartile range (Q3-Q1).
N(0,1)
Standard normal distribution.
β
The probability of making a Type II error.
C
The level of confidence for a confidence region.
Z
A variable that follows a N(0,1) OR the test statistic in a one-sample Z-test.
t
A variable that follows a t-distribution OR the test statistic in t-tests.
sp2
Pooled sample variance in a 2-Sample t-Test.
σ2
Population variance.
df
Degrees-of-freedom.
χ2
A variable that follows a chi-square distribution OR the test statistic in chi-square tests.

## Useful

The following symbols will be used in the course, but less often than those above and will not be parts of multiple choice questions on quizzes.

Symbol Definition
N
Population size. [generally unknown]
xi
Value of the X variable for the ith individual.
s2
Sample variance.
M
The sample median. [rarely used]
c
The number of columns in a two-way frequency table.
r
The sample correlation coefficient OR number of rows in a two-way frequency table.
r2
The coefficient of determination.
$$\hat{\textrm{y}}_{\textrm{i}}$$
Predicted value of the response variable (in regression).
$$\hat{\textrm{p}}$$