sample 479 c2 c3 let c10(1)=sum(c1="emmetropia" & c3="darkness") let c10(2)=sum(c1="hyperopia" & c3="darkness") let c10(3)=sum(c1="myopia" & c3="darkness") let c11(1)=sum(c1="emmetropia" & c3="night light") let c11(2)=sum(c1="hyperopia" & c3="night light") let c11(3)=sum(c1="myopia" & c3="night light") let c12(1)=sum(c1="emmetropia" & c3="room light") let c12(2)=sum(c1="hyperopia" & c3="room light") let c12(3)=sum(c1="myopia" & c3="room light") let c15=(c5-c10)*(c5-c10)/c5 let c16=(c6-c11)*(c6-c11)/c6 let c17=(c7-c12)*(c7-c12)/c7 let c20(k1)=sum(c15)+sum(c16)+sum(c17) let k1=k1+1