1. Sa pangkalahatang pahayag, ano ang isyung inilahad ng kompanya ng Philippine Long Distance?

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

a.indigo and cochineal

b.animal hides

c.silver and gold

e.cacao beans and sugarcane

answer; primary source information;