Sometimes two variables that are not relevant at all may app

Sometimes two variables that are not relevant at all may appear to be correlated. For example suppose you found a high positive correlation between income level and time spent reading books. This means that the more money you have the more time you have for reading. This means that the more you read the richer you become A third variable (perhaps socio-economic status, stress level, education level etc.) could be responsible from the positive correlation between income level and time spent reading books. Pearson product-moment correlation coefficient should be used when both variables are interval or ratio in scale. Spearman rank-order correlation coefficient should be used when both variables are ordinal in scale. Point-biserial correlation coefficient is used when one variable is interval or ratio and one variable is nominal. phi coefficient is used when both variables are nominal.

Solution

20. FALSE. because here the two variables income level and time spent on reading books are not related at all. so which one is the cause and which one is the effect can not be determined.

21. FALSE.because here the two variables income level and time spent on reading books are not related at all. there must exist some third variable.

22. TRUE. the positive correlation is due to some lurking variable or third variable which is actually making this correlation. it may happen the person whose income level is high is well educated and hence reads many books.

23. TRUE. pearsonian product moment correlation coefficient r is the measure of association between two variables which are quantitative in nature and hence measured in ratio or interval scale.

24. TRUE. when data is in ordinal scale pearsonian product moment correlation coefficient can not be used. the way out is spearsman correlation coefficient.

25. TRUE.

26. TRUE.