random variable with normal distribution

Hello, here is the problem:

A random variable obeys a normal distribution. It has a mean value equal to 100 and a standard deviation equal to 3. Find the probability that:

x < 98
98 < x < 104
x > 98

I have a slight idea i know how to find mean using mean(x) and randn(x) for some random number but no idea how to tie them together.

thank you for your time

Answer 1

[Matt J]

See the erf() command.

Answer 2

[Image Analyst]

If you want to do it empirically (like Monte Carlo), you can use this:

numberOfNumbers = 1000000; % Whatever number you want.
% From the help:
randomNumbers = 100 + 3 * randn(1, numberOfNumbers);
% Count number less than 98
count = sum(randomNumbers < 98)
fprintf('The number of numbers less than 98 = %g%%\n',...
  count * 100 / numberOfNumbers);

Repeat for other ranges.

Answer 3

[Roger Stafford]

The Statistics Toolbox function 'normcdf' is just what you need.