Answer
given,
average rent of one bed room = $1229
sample size = n = 15
Sample mean rent = $1350
Assuming standard deviation equal to $250
the test hypothesis is
H o: µ=1229
H a: µ not equal to 1229
now we know,
t = 1.875
from t- table
a=0.05, the critical value is |t(0.025, d f= n-1 = 14)|=2.14
since t= 1.875 which is less than 2.14 we do not reject H o.
So we can not conclude that the monthly rent outside San Francisco differs from that in the city