The first step here is to calculate the mean :
(70+75+80+85+90+105+105+130+130+130)/10 = 100
SD = 22.4,
one SD below the mean = (100 – 22.4) = 77.6
Only 2 values 70 and 75 are less than 77.6, hence B is the answer
(70+75+80+85+90+105+105+130+130+130)/10 = 100
SD = 22.4,
one SD below the mean = (100 – 22.4) = 77.6
Only 2 values 70 and 75 are less than 77.6, hence B is the answer
