2.3.1 In a study of the oral home care practice and reasons for seeking dental care among indi- viduals on renal dialysis, Atassi (A-1) studied 90 subjects on renal dialysis. The oral hygiene status of all subjects was examined using a plaque index with a range of 0 to 3 (0 = no soft plaque deposits, 3 an abundance of soft plaque deposits). The following table shows the plaque index scores for all 90 subjects. 1.17 1.17 2.50 2.00 2.17 2.17 1.35 2.33 1.67 2.17 2.00 1.38 2.17 1.17 2.50 2.00 1.50 1.50 1.00 2.17 2.17 1.33 2.17 2.83 0.33 2.17 1.83 1.00 2.17 2.17 0.83 1.17 2.17 0.50 1.50 2.00 2.00 1.67 2.00 2.00 1.50 2.50 2.33 2.00 2.17 2.00 1.33 2.17 2.50 2.50 2.00 2.50 2.00 2.00 1.17 1.33 1.67 2.17 1.50 2.00 1.67 0.33 1.50 2.17 2.33 2.53 1.17 0.00 1.50 2.33 1.83 2.67 0.83 1.17 1.50 2.17 2.67 1.50 2.00 2.17 1.33 2.00 2.35 2.00 2.17 2.17 2.17 2.00 2.17 2.00 SOURCE: Farhad Atassi, DDS, MSc, FICOI. Used with permission.

(a) Use these data to prepare: A frequency distribution A relative frequency distribution A cumulative frequency distribution A cumulative relative frequency distribution A histogram A frequency polygon

(b) What percentage of the measurements are less than 2.00?

(e) What proportion of the subjects have measurements greater than or equal to 1.50?

(d) What percentage of the measurements are between 1.50 and 1.99 inclusive?

(e) How many of the measurements are greater than 2.49?

(f) What proportion of the measurements are either less than 1.0 or greater than 2.49? (g) Someone picks a measurement at random from this data set and asks you to guess the value. What would be your answer? Why? (h) Frequency distributions and their histograms may be described in a number of ways depending on their shape. For example, they may be symmetric (the left half is at least approximately a mirror image of the right half), skewed to the left (the frequencies tend to increase as the measurements increase in size), skewed to the right (the frequencies tend to decrease as the measurements increase in size), or U-shaped (the frequencies are high at each end of the distribution and small in the center). How would you describe the present distribution?