hours=[28 23 29 21 24 28 30 19 8 11 4 15 13 20];
grades=[5 4.5 5 5 4 4.5 5 3.5 3 3 3 3 3.5 3.5];
[R,P] = corrcoef(hours, grades)
t_s=0.8755*sqrt((14-2)/(1-0.8755^2))

% H0 = p=0  HA = p=/=0
if(t_s> 1.761)
msgbox('We reject the null hypothesis and accept the alternative one – there is dependence between the grades and hours spent')
end
scatter(hours,grades,'filled')
ylim([2 6])
title('Correlation betwen grades and time spend on lecture')
xlabel('Hours spent')
ylabel('Grades')