Understanding Percentiles: Definition, Applications, and Calculation, Lecture notes of Quantitative Techniques

Download Understanding Percentiles: Definition, Applications, and Calculation and more Lecture notes Quantitative Techniques in PDF only on Docsity! Percentiles Lecture 8 Percentiles In this lesson: 1. Definition of a percentile and an interpercentile range. 2. Applications of a percentiles. 3. Calculating percentiles and interpercentile range. What you should be able to do: 1. Explain what a percentile and interpercentile range is 2. Give an example of when percentiles are used in your life. 3. Calculate a given percentile and interpercentile range for a frequency table with ungrouped data. Calculating Percentile Step 1: Add a cumulative frequency column if necessary Step 3: Look at the number you calculated and determine what row your desired observation is in. Step 4: Perform interpolation using the number you calculated and the boundaries of the necessary class. Step 5: To find the interpercentile range, subtract the two percentiles that you calculated. Calculating a percentile is similar to calculating a quartile or median using interpolation! Step 2: Divide the percentile you need by 100, then multiply that decimal by the total number of observations. 𝑃90 = 90 100 70 = 63 4 25 57 66 70 Cumulative Frequency Why not 179.5? 𝑃10 = 10 100 70 = 7 2, Ashopkeeper goes to a clothes fair. He records the costs of jeans. The costs are shown in the table. - Cost of Frequency Cumulative jeans (£’s) frequency 10-15 11 16-20 35 21-25 34 26-30 16 31-35 10 36-40 5 a Complete the cumulative frequency table. b Calculate Pp. ¢ Calculate Pg. d Calculate the 20% to 80% interpercentile range. 2 all, 46, 80, 96, 106, 111 b £17.10 ec £28.25 d £11.15