STDEVP(Products[Price]) : The standard deviation for values in the Price column of the Products table. Equivalent to
STDEVP(SELECT(Products[Price], TRUE)). See also SELECT().
STDEVP([Discounts]) : The standard deviation for the items in the Discounts column value, where Discounts is of type List.
STDEVP(LIST(1, 2, 3)) : 0.82
STDEVP(1, 2, 3) : the arguments are not in list form. To fix, wrap them in LIST() to construct a list:
STDEVP(LIST(1, 2, 3)).
STDEVP( some-list )
some-list (list of any numeric type)
AppSheet must be given enough context to determine what type of values some-list contains, that its contents are or will be numeric. To that end, some-list must be one of the following: a column value of type List that contains numeric values; a column list (e.g., Products[Price]) for a column of a numeric type; or a constructed list (e.g., with LIST()) of a numeric type.
Decimal: the computed standard deviation of the values in some-list.