Internal validity(casual relationship) > external validity (generalize more broadly) When results are meant to generalize and extend to a broader population: Applied research the higher the internal validity- the lower external validity - tradeoff the higher external- the lower internal. Change in response rates from 93. 5% to 68. 6% The largest sample is sometimes the most representative of the. Representativeness (external validity) - is how the sample is selected not the amount (sample size) Sample size- allows us to detect small effects and not really about external validity. If you care about ecological validity then generalizing is really important. Lab studies and eld studies tend to have the same results. As a result lab studies are considered having experimental realism. Field focusing on generalizing to other settings and other people. Easier to nd- undergrad western university students. The overall population is becoming more and more. Weird pop is used as a frame of reference.