Magali and jean-gabriel have been asked to design a study investigating happiness across the lifespan. they decide their study will involve going to the mall and asking people of a variety of ages if they are happy or unhappy. what is the most serious flaw of this design?
a. people will know that they are part of a research study and may decline participation.
b. survey data is not as valid as experimental data.
c. their results will depend on how busy the mall is.
d. they have not defined happiness or how it will be measured.

 d)They have not defined happiness or how it will be measured.

Explanation: A survey is the record that is formed on the basis of through examination and observation of any particular situation or thing. The survey carried out by Magali and Jean has a major flaw because it does not have any certain parameter for measuring the rate of happiness in people present in the mall.

Other options are not appropriate to be a mistake in survey because people will not avoid the participation, the experimental survey data is valid and dependency is not based on population of people in mall.Thus, the correct option is option(d).

answer; i believe that the correct answer to the above question is; (tariff)

i'll just take the points xd