user_status = input('would you like to find your resistor value? enter yes or no with an apostrophe on each side of the text');
You are expecting the user to type something that evaluates to a character vector. (Note that you could use the 's' option of input() so that the user does not need to put in the apostrophes themselves.)
while user_status=='yes'
You are trying to use == to compare the character vector that was input to the character vector 'yes'
For this purpose it is important that the way that MATLAB represents character vectors is as vectors of characters. So 'no' is not represented as a single undivided entity in MATLAB: instead it is implemented as ['n' 'o'] -- a vector with two positions. And then when you compare that with == to 'yes' you are effectively testing
['n' 'o'] == ['y' 'e' 's']
since characters are represented as 16 bit unsigned integers, that is the same as if you had tested
[110 111] == [121 101 115]
because 'n' is represented as the 16 bit integer 110 and 'o' is represented as 111 and so on. The exact representation of characters to numbers is as given by the Unicode Consortium, a key international standard.
You might have recognized by now that using == to compare a vector with 3 elements to a vector with two elements is not a supported operation in MATLAB. When you use == to compare vectors, either they have to be exactly the same size or else one of the two must be a scalar.