Texas Instruments TI-84 Plus - Syntax; Tol Not Met; Undefined; Validation

Appendix B: Reference Information 654
SYNTAX The command contains a syntax error. Look for
misplaced functions, arguments, parentheses, or
commas. Appendix A displays the arguments and
punctuation needed to execute the function or
instruction.
For example, stdDev(list[,freqlist]) is a function of the
TI-84 Plus. The arguments are shown in italics. The
arguments in brackets are optional and you need not
type them. You must also be sure to separate multiple
arguments with a comma (,). For example
stdDev(list[,freqlist]) might be entered as stdDev(L1) or
stdDev(L1,L2) since the frequency list or freqlist is
optional.
TOL NOT MET You requested a tolerance to which the algorithm
cannot return an accurate result.
UNDEFINED You referenced a variable that is not currently defined.
For example, you referenced a stat variable when there
is no current calculation because a list has been edited,
or you referenced a variable when the variable is not
valid for the current calculation, such as a after
Med-Med.
VALIDATION Electrical interference caused a link to fail or this
graphing calculator is not authorized to run the
application.
Error Type Possible Causes and Suggested Remedies