Identify the correct answer to "X" for below questions:

1. When a given value for the response variable, we can use the least square regression line to predict the value of the "X" variable
2. When testing correlation for two quantitative variables: Ho:p=0 bs Ha:p<>0, the test statistic has a "X" under the null hypothesis
3. If the least square regression line has slope B^1 = 6 and two x vallues differ by 3, the predicted difference in y-values is "X"