A fish-and-chip shop records mean daytime temperature ttt °C and daily sales S S\,S pounds on 10 randomly selected summer days. The correlation coefficient is 0.670, with a one-tailed p-value of 0.017. The regression line is S=5148+141tS=5148+141tS=5148+141t.
Test at the 5% significance level whether there is evidence of positive association.
Identify the explanatory variable and justify your choice.
Interpret the gradient.
Explain why the result does not prove that warmer weather causes higher sales.