Researchers were interested in testing whether there was a difference in the % particles filtered for KN95 masks vs. double masking using a surgical + cloth mask. Using the results below, what would the degrees of freedom be?

Researchers were interested in testing whether there was a difference in the % particles filtered for KN95 masks vs. double masking using a surgical + cloth mask. Using the results below, what would the degrees of freedom be? KN95 Double mask Mean % particles filtered @ Sample standard deviation\" *note data not real " a. 19 b. 9 " c.10 d. 28