The estimated standard error of difference may never assume a negative value. (True or false?)

The estimated standard error of difference may never assume a negative
  value.
 
  Indicate whether the statement is true or false

Question 2

The final goal of the paired t, is to
 
  a. test the hypothesis of association
  b. test the hypothesis of difference
  c. match the independent and dependent variables
  d. match the independent and control variables

Question 3

With any t test, independent or paired, the more subjects there are being
  measured
 
  a. the greater the number of degrees of freedom
  b. the fewer the degrees of freedom
  c. the greater the alpha level
  d. none of these

Question 4

The estimated standard error of difference estimates the value of the
  population mean.
 
  Indicate whether the statement is true or false

Question 5

Is this sample representative of the population at large?
 
  The average sentence (in months) for homicide is 227 (Gaines & Miller, 2003).
 
  A sample of inmates from a certain prison, all of whom having been convicted of homicide, was selected and their sentences calculated. The sentences follow: 200, 225, 197. 256, 300, 158, 220, 226, 230, 215, 237, 223, and 243.
 
 
 What will be an ideal response?