ClearAll;

n = 8;

a = {0.387, 0.723, 1.524, 5.203, 9.539, 19.182, 30.058, 
          39.44};

T = {0.241, 0.615, 1.881, 11.862, 29.458, 84.014, 164.793, 
          247.7};

x = Log[a];

y = Log[T];

xmean = (1/n)*Sum[x[[k]], {k, 1, n}];

ymean = (1/n)*Sum[y[[k]], {k, 1, n}];

sigmaxy = (1/n)*
          Sum[(x[[k]] - xmean) (y[[k]] - ymean), {k, 1, 
              n}];

sigmax = 
        Sqrt[(1/n)*
            Sum[(x[[k]] - xmean)^2, {k, 1, n}]];

sigmay = 
        Sqrt[(1/n)*
            Sum[(y[[k]] - ymean)^2, {k, 1, n}]];

m = N[sigmaxy/sigmax^2]

q = N[ymean - m*xmean]

corr = N[sigmaxy/(sigmax*sigmay)]

xsi = 10^q

etha = m

p0 = 
        ListPlot[Table[{a[[i]], T[[i]]}, {i, 1, n}], 
          PlotStyle -> PointSize[0.03]];

p = 
        ListPlot[Table[{x[[i]], y[[i]]}, {i, 1, n}], 
          PlotStyle -> PointSize[0.03]];

g = 
        Plot[m*t + q, {t, Min[x], Max[x]}, 
          PlotRange -> {Min[y], Max[y]}];

Show[p, g]