Mean of variables question, please help!!?

Question

If X~N(mean of x variables, variance^2) what percent of the data falls between ‘the mean of x variables’ and ‘the mean of x variables + standard deviation’

a) 0.34
b) 0.475
c) 0.5
d) 0.95

Answer 1

The question is poorly worded. It should read more along the lines of:
For a normally distributed data set, what portion of the data falls between ‘the mean of x variables’ and ‘the mean of x variables + standard deviation’

One thing you should simply memorize is that 68% of a normal distribution lies between -1 std dev and +1 std dev. The mean, of course, is right in the middle of that. Your problem only asks for how much is between the mean and +1 std dev, so it will be half of the 68%, that is, 34%.