My guess is that you've probably misplaced some parentheses. Check them very carefully. And you don't need the @(t) - you can simply do
t = [2993;3975.9;5063;6150;6919;8192.7;8862;10240.9;11488;12409.63;13545]
f = (2.2/9500).* ((t/9500).^1.2).*exp(-((t/9500).^2.2))
g = 1 - exp(-((t/8900).^2.2))
results = f - g
% Plot things below.
plot(t, f, 'b.-', 'LineWidth', 2, 'MarkerSize', 20);
hold on;
plot(t, g, 'r.-', 'LineWidth', 2, 'MarkerSize', 20);
grid on;
legend('f', 'g', 'Location', 'north');
