Is the calculation accuracy low in MathCAD compared with Maple?

The differences you see are due to numerical approximations (when you use a numerical evaluation with '=').

If you let Mathcad solve your problems symbolically you get exact answers.  In your examples with Maple, it determines the solutions symbolically, then (when needed) it converts the answers to numerical answers.

The example above from Fred appears to show an exact match between the numerical approximation and the symbolical solution of the integral over the normal distribution function. But when you tell Prime to show the result with sufficient decimals (15...) then you see the answer is not eactly 1:

(This was done with Prime 4.0 express, hence I cannot show the symbolic result.)

In Mathcad 11 (which uses Maple as its symbolic engine) you get:

(If I tell Mathcad 11 to show 15 decimals, it still shows 1 as a numerical result. To show the 'error' I had to subtract 1 from the integral).

Apparently the numerical approximation is done differently from Prime's algorithm, or the settings are different, resulting in a somewhat better approximation of 1 for the integral.

Note that the symbolic result is exact.

Success!
Luc