Answer:
2. Matched-sample t test
Step-by-step explanation:
The matched sample t test (or matched sample t test) is used when sample units from two data sets can be presented in form of pairs. Eg - Same people given a treatment, their before & after versions illustrate paired data sets. The test is used to check whether the two sets of paired data, have statistically significant different means.
Letting new variable 'd' as the difference between the two paired data series, x1 & x2. So, d = x1 - x2. 't' is calculated as undermentioned :-
t = (d - M ) / [ sd /sqrt(n) ] ;
where M = assumed difference {here it is difference in blood pressure before & after job, i.e 55 - 40 = 15}