Chapter 7 - Correlation

Calculate the correlation coefficient between X and Y and comment on their relationship

Calculate the correlation coefficient between X and Y and comment on their relationship:

Calculate the correlation coefficient between the heights of fathers in inches (X) and their sons (Y)

Why does rank correlation coefficient differ from Pearsonian correlation coefficient?

Interpret the values of r as 1, -1 and 0.

List some variables where accurate measurement is difficult.

Measure the height of your classmates. Ask them the height of their benchmate. Calculate the correlation coefficient of these two variables. Interpret the result.

Collect the price of five vegetables from your local market every day for a week. Calculate their correlation coefficients. Interpret the result.

Can simple correlation coefficient measure any type of relationship?

Does zero correlation mean independence?

When is rank correlation more precise than simple correlation coefficient?

Does correlation imply causation?

Can r lie outside the -1 and 1 range depending on the type of data?

Why is r preferred to covariance as a measure of association?

If precisely measured data are available the simple correlation coefficient is

(i) more accurate than rank correlation coefficient

(ii) less accurate than rank correlation coefficient

(iii) as accurate as the rank correlation coefficient

Of the following three measures which can measure any type of relationship

(i) Karl Pearson's coefficient of correlation

(ii) Spearman's rank correlation

(iii) Scatter diagram

If rxy = 0 the variable X and Y are

(i) linearly related

(ii) not linearly related

(iii) independent

If rxy is positive the relation between X and Y is of the type 

(i) When Y increases X increases

(ii) When Y decreases X increases

(iii) When Y increases X does not change

The range of simple correlation coefficient is

(i) 0 to infinity

(ii) minus one to plus one

(iii) minus infinity to infinity

The unit of correlation coefficient between height in feet and weight in kgs is

(i) kg/feet

(ii) percentage

(iii) non-existent