Solution
"r= \\frac {(n(\u2211xy)-(\u2211x)(\u2211y))}{\\sqrt{([n\u2211x^2-(\u2211x)^2][n\u2211y^2-(\u2211y)^2]})}"
"\u2211xy=257.06"
"\u2211x= 75.3"
"\u2211y= 68.4"
"\u2211x^2 = 289.59"
"\u2211y^2 = 241.86"
"n=20"
"r= \\frac {(20*257.06-75.3*68.4)}{(\\sqrt {([20*289.59- 75.3^2 ][20*241.86- 68.4^2])} )}"
"r= -0.06707"
The test statistic:
"t= \\frac {(r \\sqrt{(n-2)})}{\\sqrt{(1- r^2 )}}"
"t= \\frac{(-0.06707 * (20-2)^(0.5)}{\\sqrt{(1- (-0.06707)^2 })}"
"= -0.2852"
The p-value given "t = -0.2852" and "n-2=20-2=18" degrees of freedom:
"p value=0.7789"
Answer: t value = - 0.0670
The correlation is not significant since p value (0.7789) > significant level (0.05)
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