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If 40 is the 50th %-ile,63 is the 95th %-ile,what's the SD? What's the %-ile for 41,42,43,44,45,46,47…?
Klout gives people "influence" scores from 1-100. 40 is average. 63 is the 95th percentile. N.B.: The scores are logarithmic! Klout doesn't reveal what the Standard Deviation is, or what percentile different scores represent, but someone clever ought to be able to calculate it, based on the assumption that "influence" falls in a standard distribution. You can go to Klout.com for more info.
I don't have a handy z table. In fact, I'm embarrassed to say, I didn't follow the math of your answer. Could you please provide me with some more values? At least up through 47 or 50?
1 Answer
- KevinMLv 78 years agoFavorite Answer
The Z-value for P=0.95 is Z = 1.64. So in your question, (63 - 40) = 23 corresponds to a Z-value of 1.64. So:
Std Dev = 23 / 1.64 ~= 14
You can use this with a Z-table to determine the corresponding probabilities for 41, etc. For example:
P(x<41) = P(Z < 1/14) ~= 52.8%
P(x<42) = P(Z < 2/14) ~= 55.6%
etc...
Ed: You can't do this problem without a Z-table or a Z-calculator. A Z-table is required to calculate the standard deviation. If you don't have one, here's an on-line Z-table:
http://lilt.ilstu.edu/dasacke/eco148/ztable.htm
Since the 50th percentile is 40, the mean is 40. And since the 95th percentile is 63, P(x-x0 = 23) = 1.64 (from the Z table). So the standard deviation is 23 / 1.64 ~= 14.
Now you can calculate all values based on this Z value and the table above.
