ECON 2B03 Lecture Notes - Lecture 5: Frequency Distribution, Skewness, Interquartile Range

• School: McMaster University
• Department: Economics
• Course: ECON 2B03
• Professor: Jeff Racine

Document Summary

The median divides data into equal halves: odd number of observations: Median = middle observation in the ordered array: even number of observations: Median (n odd take the middle observations): Median (n even take the average of the two middle observations): Overall range: equals the difference between the larges and smallest observation in a data set (in r we use the range () function) Interfractile ranges: measures difference between 2 values in the ordered array (cid:894)(cid:272)alled (cid:858)f(cid:396)a(cid:272)tiles(cid:859)(cid:895) Quartiles: divide the array into 4 quarters. Interquartile range: difference between 3rd and 1st quartiles (contained middle 50% of data) In r we use the iqr () and the quantile () functions. A f(cid:396)e(cid:395)ue(cid:374)(cid:272)(cid:455) dist(cid:396)i(cid:271)utio(cid:374)(cid:859)s deg(cid:396)ee of distortion from horizontal symmetry. Pea(cid:396)so(cid:374)(cid:859)s (cid:894)fi(cid:396)st(cid:895) (cid:272)oeffi(cid:272)ie(cid:374)t of ske(cid:449)(cid:374)ess is (cid:894)(cid:449)e (cid:449)a(cid:374)t to k(cid:374)o(cid:449) is it +/-- ?) Skewness = mean model / standard deviation. An alternative (more popular, default in r) movement-based measure is given by.