Which of the following is not a factor involved in the process of evaluating an observational study?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

For a science project, a high school research team conducted a survey of local air temperatures. based on the results of the survey, the found that the average temperatures were around 10 degrees higher than expected. this result was wrong. the trouble with the survey was that most of the locations were exposed to direct sunlight and located over asphalt or sand, which resulted in higher temperatures than normal. this is a classic example of an error in which phase of inferential statistics?

1/4x+5=3/4. i can't get access to the answer to this question! and, my request on "contact us" will not go