Dr. salahma conducts a study on teenagers and product preference. in his study, he begins with a diverse sample of 13-19 year olds. however, after the first few trials of the experiment many of the 15-year-old boys in the experiment stop responding to the questions and choose not to participate in a follow up session. dr. salahma needs to be concerned about __

Selective Dropout

Explanation:

According to my research on different research concerns and common issues, I can say that based on the information provided within the question Dr. Salahma needs to be concerned about Selective Dropout. Like mentioned in the question this term refers to the tendency of some individuals to drop out of a study. Which can make the results of that study completely invalid. Which is what seemed to have happened in the first few trials of the experiment mentioned in the question.

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Explanation:

The format for the equation of a circle is (x-h)^2+(y-k)^2=r^2, where (h,k) is your center and r is your radius. All we have to do is substitute the correct values, giving us the equation (x+2)^2+(y-1)^2=4