Question 1179000
The following are the values of {{{d[i]}}} = temp after - temp before:

-4.2, -4.1, -2.9, -4.4, -4.3, -0.5, -3.1.

==> {{{d[m] = -23.5/7 = -3.357}}} and {{{s = sqrt((1/(n-1))*sum((d[i] - d[m])^2, i=1,7)) = sqrt((1/6)*sum((d[i] +3.357)^2, i=1,7)) = 1.395}}} to 3 d.p.

Now 

{{{H[0]:  d = 0}}}  and {{{H[a]: d< 0}}}, with 5% significance level.


Using the test statistic  {{{t =(d[m]-d)/(s/sqrt(n))= (d[m]-0)/(s/sqrt(n)) = (sqrt(n)*d[m])/s}}}, one obtains {{{t = (sqrt(7)*-3.357)/1.395 = -6.367}}}.

The critical t-value is given by {{{t[0.025] = -2.447}}} using https://stattrek.com/online-calculator/t-distribution.aspx.

Since {{{t = -6.367 < -2.447 = t[0.025]}}}, we reject the null hypothesis and conclude that the drug reduces the body'stemperature.