define brefily the concepts "necessary condtion" and "sufficient condition" and give two examples for each ​

  consider  the  following scenario,  then describe  how  you might conduct  a  study using  ansrs,  convenience sample, and a  voluntary response sample.  you  are  interested  in  parents'  opinion  of the  war  in  iraq.  your population  is  parents  of  high school students.  your question  is, "do you  believe that the  war  in 

Which element of a health-related website would suggest that the site may not be credible or reliable?

hyperlinks to other fitness, nutrition, or medical sites
tips for achieving instant positive results or an instant cure
details about a recent study on a medical issue or condition
safety warnings related to the information that is presented