# Basic arithmetic question

I have to find $80\%$, $60\%$, $40\%$, $20\%$ and it's values of a range of scores.

For one range, my values go from $2$ to $8$ (mean will be $5$ which means, $50\%$ of that range's value = $5$)

For second range, my values go from $3$ to $15$ (mean will be $9$ which means, $50\%$ of that range's value = $9$)

How do I come up with some formula to find $\%$ and values at $80\%$, $60\%$, $40\%$, $20\%$ and make it dynamic (I can plug in any range and it would give me values at those $\%$)

Thank you

• If the range runs from $a$ to $b$, you need to compute $a+{n\over 100}(b-a)$ for $n=20, 40, 60, 80$. You then need to count how many scores you have in each interval. This is usually best done with a spreadsheet. – Per Manne Aug 14 '12 at 18:18
• Wow...that works. Thank you I am not using Excel but using a different software (programming) so this would be possible in that too..Thank you – user1569220 Aug 14 '12 at 18:41
• Note the 50% point is the median not the mean. You would not use the mean when asked for the 50th percentile. – Michael R. Chernick Aug 14 '12 at 19:16
• Oh you are right...median not mean. 50th % is median... – user1569220 Aug 23 '12 at 2:48