I have some data that I need to find 50% value for. The chart consists of the period (days) as X axis values and percentages as Y axis values. I was trying to find a way to determine the 50% value on a trend line for each treatment. Is there any easy way to do that without going through modifying the formula and applying it for each treatment?
I attached a pic for one of the treatments I want to find 50% value for.
Thank you in advance for your assistance.
Dear Mustafa,
A direction in MS-excel!
The BLUE line:
INTERCEPT= INTERCEPT(known_y's,known_x's)
SLOPE= SLOPE(known_y's,known_x's)
To estimate Y=50 use:
= (50-INTERCEPT(known_y's,known_x's))/(SLOPE(known_y's,known_x's))
For the RED line, follow as above.
I do hope it will be what you want. (an example is attached).
Raoof
for eg; percentages - 11 values, don't you just average these ?96+36+22+23+14+77+39+42+25+89+58
= 47% maybe I'm wrong, but you can easily do this formulae in excel if that is correct, but maybe this is not what you mean by 50% value maybe you are meaning the median not the average
Hi Deborah,
Thank you for your response. I think that I did not describe the issue correctly. I can not average them because I am looking for the X value that crosses 50% Y value on the "Trend line", not the original curve. Is there any easy way to find this value?
Thanks again for your comment.
Mustafa
Dear Mustafa,
A direction in MS-excel!
The BLUE line:
INTERCEPT= INTERCEPT(known_y's,known_x's)
SLOPE= SLOPE(known_y's,known_x's)
To estimate Y=50 use:
= (50-INTERCEPT(known_y's,known_x's))/(SLOPE(known_y's,known_x's))
For the RED line, follow as above.
I do hope it will be what you want. (an example is attached).
Raoof
Dear Mustafa,
Please check the article attached herewith. It may be useful for you.
http://spreadsheetpage.com/index.php/tip/chart_trendline_formulas/
Thanks Raoof,
It looks helpful for some values but not for all. In your example the value of 50 for Y1 looks reasonable, but not the value of 50 for Y2. Don't you agree? 50 for Y2 should be something around 5.5 or so.
Thanks,
Mustafa
You are right!
Not assigned the X value to the Y2 series.
See the attached with a bit modification.
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